I think it depends on the bike. Backpack blocks my view in my mirror on my road bike, sticks up in the wind and blocks airflow on my back. On my more upright, slower commuting rig I don't mind, although having a rack makes it a moot point on that bike.

I'll echo the Ortlieb pannier recommendation. Also the Racktime brand racks, which are the lower cost brand from Tubus. I have the Add-it model on two bikes along with a pair of QL3 office panniers. Not cheap, but they are built like tanks and hold plenty. I also have one of the Ortlieb QL3 Vario backpacks that easily swaps between backpack and pannier modes. I rarely use the latter for commutes, but it still finds occasional use when I need to walk a bit, or need to tote the work laptop around. I did have to purchase another QL3 adapter to have both racks ready to carry, so a bit like Festool if you know the tool brand, that once you're hooked... For the most part my purchases were clearanced or returned items, so if you are patient you can outfit yourself for not too much.

Anyway, the office panniers serve 95% of my needs. On Mondays I usually pack in five shirts and maybe a pair or two of cleaned and pressed pants to cover me for the week. I keep extra pants on hand just in case. During warmer months, I usually only need both panniers on Monday, with one able to hold my lunch, electronics, underwear, and towel for the work shower. I also use a frame pack (Revelate Designs Tangle model?) that mounts to the top tube and uses the main frame triangle. It holds a CO2 pump, tube, patch kit, multi tool, trauma kit, locking chain, and keys. I found the frame bag to be perfect for holding items always needed, so whatever the bag I don't find myself without the basics. During the colder months, I use both panniers for all the other needed garb. I keep toiletries at work.

I am lucky at work that it is a secure campus with covered outdoor bike racks, so I can leave my frame bag attached. It is so secure that plenty of other riders leave lights, electronics, and bikes unlocked. I'm not that trusting, but it is nice to know.

When I do use a backpack I'm partial to the Osprey Manta model. Comes with a bladder and drink line, which is nice. It barely gets any use for commuting, mostly being used for family rides. In my neck of the woods it gets too hot for a backpack and I also don't like the way it throws off my balance when weighted down. Otherwise, the Manta is my go to pack for non-bike travel.

I haven't seen the Klick Fix product line before, thanks for sharing!

About evenly split, sort of
 

In tallying up the responses, as near as I can tell, I come up with 12 for panniers/trunks, 11 for backpacks, and 10 for other preferences (like messenger bags, backpacks on rack or in boxes, etc.). Of course, what this tells me as was said by four or so commenters is that I have to figure it out for myself, which is obvious. But this thread has given a lot of great things to consider, solid information, products I never knew existed, and pictures and videos. I thank all who have contributed and who may yet contribute.

Yep, like most questions on the internet the answer is usually it depends. I've accumulated a pair of panniers, a rack, trunk bag and several backpacks over the years and prefer a backpack but use the others when they're a better solution using experience gained by trial and error.

Well, I made my decision, and I decided to go with a trunk/pannier setup. I got the Topeak MTX DX trunk with fold out panniers. It, along with the Explorer rack, was in my budget. I love it. The panniers hold a surprisingly amount of cargo. I love the quick release feature of this trunk and that it has a shoulder strap. It definitely feels great to ride without a pack/weight on my back, I love it.

Thanks to all who contributed to this thread.

I feel like the backpack makes me hot. I strap my backpack to my front porteur rack or rear rack. I also have a pannier basket that fits most of my backpacks that is a good option.

I also go a panner style messenger bag (with hooks). This is a decent option. Not perfect for me, because the messenger isn't my every day bag and doesn't match my own personal style. I recently got pannier that I have used a luggage lock to attach to my rack for security. But I am not leaving them on my bike for more than a few hours.

I have a work backpack and a purse. These currently go to my porteur rack. I take this with me.

I can see why people like the Ortlieb bags, but they aren't practical for me all day!

Day three and I do not think that I will ever go back to a backpack. I sure enjoy the freedom of no weight on my back.

Those look really nice. Don't suppose you have a pic of it on your bike? I'm having a hard time visualizing how big those dimensions really are.

That would really solve my issues...I want to put my bike on a bit of a diet...ditch the racks/panniers. I really only need enough space for a change of clothes, a sandwich, spare tube & a couple tools.

So glad I used panniers today so I don't have a sweaty back.

I commute with the topo designs mini mountain bag which holds just enough stuff for a day of work