If you can live with the slightly wacked weight distribution, a rack, hands down.
I try all different things to keep me somewhat non-drippy in the summer months because
I use a backpack most of the time, and I have come to: a wet T-shirt placed in the freezer
for about 1/2 hour before my ride and a one of those freeze packs in the backpack itself.
My ride is only 4 miles in, so that works out pretty well