I'm 6ft 3ins and 205lbs. The roads around here are pretty crappy, and as a nice compromise, I run a 25c in the back and a 23c up front. There's a couple of reasons for this. Firstly, you can run slightly less pressure in the back. This is good because 1) Gives you more cush 2) Lower pressures allow the tire to conform to the road surface better, giving you better traction, grip and control. Secondly, you have more weight on the rear tire so it makes sense to have a larger tire on the back, and seeing that it's the tire being driven, a larger contact patch on the rear means more power to the ground.

I can't say I've noticed much difference in 'rolling resistance' or speed or anything when I've gone back to a 23/23 - I've just found that as a big guy the combo of 23/25 seems to work really well. I have about 600mi on a set of 23/25 Hutchinson Fusion Long Distances, and they seem to be holding up - definitely worth a look.