With bags, smaller is sometimes better, but less is never more.

I have an extensive collecton of trunk bags, panniers, messenger bags, Camelbaks and assorted non-cycling type bags (my wife has had the nerve to call them purses) in all shapes and sizes.

Which one I use depends on what I'm carrying, which bike I'm using, how far I'm going, whether or not it's raining, etc.

My small Camebak is more comfortable than my large one if I don't have a lot of stuff. If I have just my laptop, I use the small Camelbak because it's more comfortable.