Originally Posted by Lone Ranger
At 215 lbs, I have had both on the same bike (Lemond Zurich all steel) and noticed a bit more comfort on the 25s and a bit less rolling resistance on the 23s. Nothing huge in either case. If you are unhappy with the comfort of your bike, it might be worth trying the 25s. Otherwise, I don't see any real reason to change.
A larger tyre (25c vs. 23c) has less rolling resistence at the same air pressure than an identical but narrower tyre. This is because the larger tyre will have less sidewall deflection as compared to the smaller tyre when they are identically loaded. Independent testing of rolling resistence factors for bicycle wheels, pretty much discount the contact between the tyre and the road surface as contributing much to rolling resistence. The sidewall fexing as the wheel rotates and the wheel hub bearings contribute most to the resistence.