Well, my LBS just got a new batch of Chrome messenger bags, all the way up to the big Kremlin size (although none of their backpacks). So they've got me thinking...

I have a couple normal-sized bags, one military issue and one Swiss Army bag. Both of them carry what I usually take to work, although they kinda suck on the bike. They don't really stay in one place, so I'm always pushing them back to where they're supposed to be.

I have a backpack that's designed more for carrying a laptop and some other stuff. It's good for what it is, but it's getting old enough that I'm worried about the straps staying attached, and computer-specific features like the laptop sleeve take up extra space that could be used for, say, an extra pair of shoes or other clothing. I've also got an issued ALICE pack (think 1970's-era military bag ), which really isn't bad, but I'm trying to keep a relatively low profile, especially with an upcoming trip to Europe.

I commute on my CAAD8 just as often as on my city bike, and the commute itself is under ten minutes. I don't really see a need for a rack & panniers at this point.

So, I'm trying to decide whether to get an honest-to-god messenger bag or a good-sized, cargo-friendly backpack. I'll be riding with it to work and sometimes using it as carry-on luggage.

I mentioned the Chrome bags to my sister. She said that her husband uses a messenger-style bag all the time, but it's uncomfortable for him since it mostly hangs off of one shoulder. I'm a reasonably sturdy guy, and I often switch my bag from one shoulder to the other as needed, but I'm now just hesitant enough to not buy a new bag right away.

Which do you guys prefer, considering utility, comfort, etc? Why get one instead of the other -- what does a messenger bag do that a backpack can't, and vice versa?