EricL

This is my first real post and it's going to be a bit long so bear with me. Looking for some advice from those with real world experience. I commute 22 miles each way with a messenger bag over my shoulder. In that bag I carry: work clothes, a small cooler full of food, map, tube/levers/patch kit, a couple of tools, wallet/phone/keys etc. and the occasional book or dish or cup.
I'm 6'1" and 190lbs. and I commute on a Trek 2.1. The ride is fairly smooth but I do have some rough spots (If you know Denver and you've been on Bear Creek between Lowell and Sheridan you have an idea) I like the bag because I can control the weight over the rough spots that I can't avoid and because it's mostly behind me so it cuts down on the wind resistance, faster ride. I've just had this notion in my head that the bike won't get as beat up if I wear a bag as opposed carrying a rack and panniers, and the panniers will slow me down.
But .... I wonder how much of that is true and how much is my imagination. I do prefer riding with nothing on my back, and my lower back is kind of messed up, has been for a long time.
Looking for the best combination of comfort and stability with the least amount of wear and tear on the bike.