Quote Originally Posted by shootingstar View Post
And shoulder strap type bags, ie. messenger bags aren't useful to me since I have a small body frame and I find the bag weight shifts around my body and hinders my cycling. It actually is so bothersome, it slows me down because I have to fling the bag out of my way. Useless.
I'm barely 4'11" and a lightweight and don't have the problem with having to fling my messenger bag around, as long as it has a waist strap to stabilize it. I also much prefer a messenger bag over a backpack because I can adjust it more. Maybe it's just me, but with a messenger bag, the weight is comfortably distributed across my back, but with a backpack, it's all on my shoulders.

I did specifically exclude certain bags from the running because the dimensions wouldn't work for my torso (I don't want a bag that's 20" across if it isn't going to hold much), but the main reason I'd go for panniers is back sweat.