I also feel that backpacks offer more organization for small items which is a big plus IMO. Also I carry a lot of electronics like a MacBook Air, an external hard drive, a camera, a Kindle, etc and I never feel comfortable with those things in my panniers. The roads are way too rough around here. I use 700x38 tires, a steel frame and rack, and I unload when approaching a rough spot I can't avoid, but still I am not comfortable leaving electronics in a pannier like that. I think my muscles and bones offer more shock absorption and protection for my valued electronic gadgets. Also I didn't realize sweating was such a problem for so many people. I sweat, too but it's bearable.