I prefer either a single or double panniers over a trunk rack or a backpack for commuting.

Go with panniers. [poppie]On this issue there can be no debate![/poppie] I used a backpack for years when I was younger and stupider. But now I have seen the light. I will never wear a backpack again. Panniers are the way to go.

Once you go pannier, you never go back....pack.

Depends on lifestyle, commute distance and physical strength and weather.
I have commuted for about 10 years now (Can hardly believe it myself). I am now using the courier bag, a Timbuk2 one. I have used everything from paniers to backpacks to courier bag.
Why do I recommend the courier bag.
You can fit more into it, it is more flexbile and it has pockets for all the nice bits and pieces, a key holder, place for your wallet, tools etc. It is also the only way I could easily bring my work stuff and my change of clothes around.
I did not find the backpack great, I also did not find paniers great as I use a Sirrus and the weight all on the back was too much then installled low loaders and used these for two years with Ortlieb paniers on the fornt. Pain in the ass balancing weights each day, bought the courier bag, never looked back. Using it now for 18 months 5 days a week plus holidays, weekends away etc.
HOWEVER, I live in Dublin, Ireland, while we get rain and cold (no snow) we do not get really hot weather. If we got really hot weather then I may be singing a different tune
Hope this is of some use to you. No right or wrong answer on this one...

I use a pannier for commuting. A backpack for short errands into Wynnum. For some errands I just take a bag from the store and hang it from the bars. And keep a couple of bungie cords in your pannier in case you need to carry something big.

I once rode home with an 8 week old labrador puppy in my backpack.

I once had a timbuk2 one too. But it got too hard to say.

I use a back pack because it is what I have and it fits what I want to carry. I am looking for a set of panniers and or a trunk. I put a rear rack on my bike so I could do this but just haven't had the disposable income to buy it yet...and I am not sure of what I want yet. I need fenders still too and I think they will be first. I have been looking at this cannondale pack. Anyone using it?

Messenger bags seems to be the consensus over backpacks -- is that style or functionality??

Also, how come I never see a bike messenger in the city with panniers?

Time. Messengers need to get on and off fast, and taking panniers on and off would
slow them down. And they can't leave them on as they would likely be stolen.

Plus, panniers look geeky. ;-)

I like to grab a bag that looks similar to what other people are carrying. Msger bags and packs are more portable and you can use them for non-biking days. No switching bags non-sense between biking and non-biking days.

Wind resistance is another factor. The newer packs seem more aero and lighter

I commute with a messenger bag too (timbuk2 too!). It's just convenient to be able to go to the store on the way home, or to multiple locations. It carries enough, but it's true that on the days I have to lug around my laptop, I'm not to happy about it. It's both function and style, I think. I like how it hangs lower on the back, so I don't get that sticky sweaty upper back. I can easily reach into my bag to get stuff out without having to swing it around, and it closes securely with the large velcro tabs even without using the clips. If you get a messenger bag, make sure it has the cross strap to secure the bag properly while riding. And I'd recommend a brief case style handle. I don't have one, and that's the one thing I wish I ordered on my bag.

In addition to the center of gravity comments others have made, having extra weight over the rear tires (as opposed to centered) increases breaking effectiveness. In quick stops, weight shifts off the rear tire, dramatically decreasing it's breaking power. The extra weight helps hold the rear tire down, so the front break doesn't have to do as much work.

On my way to work in colder weather I use the soft backpack full of my clothes (business casual attire) and shoes along with First Aid kit, tools, lunch and at times my laptop on my back. I made the pack to fit the rear bike rack so that it fits real snug with straps for the ride home. On the way home I put the Camelbak pack on my back and my backpack on my rack. Now I use a the new kind of bowling ball bag ($20.00)with lots of pockets and nice compartments to put stuff. I have to walk a tad and the bag is just right and looks good as well. Now I need a Bright Bowling shirt and I am complete :)

Key advantage of backpack: it's free, since presumably you already got one. One can only afford just so many $50 and $100 accessories. :)

And I bet they mess up your sleek/clean/minimalist fixie look. :o

The messenger bags leave more of your back exposed on hot days. I've gone to a trunk bag on a rear rack because of that. I really don't carry enough for panniers, but do realize that they would lower the center of gravity of my total load. When a trunk bag is heavy, you have to remember to keep your bike fairly vertical when you stop, or it could start to lean too much, and the wheels start sliding to the side. At least that's what happened to me. If I get really organized, I imagine I could switch from the larger backpack I sometimes carry to just putting a few things in my Camelbak M.U.L.E. without the bladder.

i'd have to vote for the messanger bags too. I use a manhattan portage bag, comparable to timbuk2. They last longer than backpacks because of the lining and are water proof and can carry a larger load. I don't use panniers because in brooklyn, whatever can come off easily with screws will most likely be stolen, so the less on the bike the less to steal. and here in NYC, we need a LARGE chain, so it's uncomfortable to have the chain around your shoulders or waist and have a backpack. oh...and panniers do look geeky...sorry for being superficial, but can't help it...

Most definitely a backpack. Plus, I would shudder to think what a bumpy ride would do to my laptop if it were in those saddlebags. With a backpack, I can stand up to cushion the bumps. Plus, I have all my gear (keys, ID, cell phone, etc..) attached to the daisy chains for easy access.

http://www.panniers.com/panniers/rt6...p?color=&site=

I bought the RT 60. They have lots of room and can be easily carried as a back pack.

Catrike Road #116.
"Cats just don't feel safe on a moving bicycle, no matter how much duct tape you use"--Author unknown

for those of you that carry your laptops and not a lot of other things, i'd take a look at booq bags. I have one for my laptop and usually double as my regular bag. can be worn either as a backpack or messenger. pretty beefy protection for the laptop and fits quite a bit for it's size. One of my favorite bags. booqbags.com highly recommended

I sweat tons, and found myself unprofessionally drenched when I biked to work with a backpack---even if I biked pretty slowly on a pretty cool day. I've since switched to the Breezer BizPannier and find myself a much happier commuter. I particularly like that it comes with a shoulder strap and that the rack attachment hardware zips off. It is an attractive enough bag that I use it as a shoulder bag on days when I take the train to work or when I travel for business. Also has laptop sleeve and rain cover. One warning only: at 17 inches wide there wasn't sufficient heel clearance due to the relatively short chainstay on my road bike. Purchased the Jannd Expedition rack, which is three inches longer than your typical rack, and that pretty much solved the problem. I'd take a look at the Arkel Bug if you think heel clearance may be an issue. The Breezer bag is actually made by Intertia Designs, and you can buy it for a few bucks cheaper through them, but I find the version you can get through Breezer far more attractive. Hope that helps.

I tried panniers for commuting, but had several problems.

First, the good news is they made everything feel wonderfully lighter. When I stand up to pedal, I don't feel weighed down at all. I can see why they are vastly superior for touring. I may use them again in the summer when keeping my back cool is a priority.

The problems: makes the back of the bike feel really heavy, especially when you go over a bump and worry that your rear triangle is gonna snap off (I'm sure this is an illusion, but disquieting nonetheless). That was with 32 mm tires on my fixie frame. My panniers don't have a convenient way to carry them around when not on the bike, so that makes them hard to use for grocery shopping and such, since I don't want to leave them on the bike where they might be stolen.

I have used over the years, Courier Bags, Backpacks & panniers for commuting.

My opinion is that a Pannier on the side that the traffic passes you is best. When I first switched I'm sure that the drivers were giving me more room. Also when commuting at night I put a light on the pannier making me appear much wider than I actually am.

As I have a rear LED light on my helmet as well, i'm sure a backpack would obscure the view of it.

I felt so free when I switched from backpack to pannier - it was like being unchained, like being nekkid.

That's a bowling bag? At first glance, thought it was a Carddice saddle bag! Kuhl

Few years ago I started commuting with a cheap hydration backpack, and loved it. Cheap, very convenient, I could fit everything I needed into it. It had a dark side though - my back would get sweaty in no time when carrying it.

When the bladder in my backpack developed a leak, I decided to look for alternatives. Since I already had rear rack, I bought pannier bag. It was largish, and I used only one. Bike handled OK with asymetrical load, and since I had the bag on the traffic side, I thought that cars were giving me a bit more space when passing.

I was somewhat concerned about weight distribution - I rode in a very upright position, with handlebars higher than saddle, hence most of the weight was on the rear wheel. I decided to try front panniers; I got rack and bags from Nashbar (I think) and never looked back. The bags are not as convenient to carry off the bike as a backpack, and I had to go back to using water bottle (sigh), but for me it was definitely worth it. My back can breath, bike handles better because of lower center of gravity (it's more stable, without losing much agility), I can wear reflective vest (I used to drape it over the backpack), I can easily access my jersey's rear pockets...

That's my story. Perhaps investing in a better backpack would help with sweaty back, but I don't hike after riding...

Others may know more though.