Hi, I suspect you will generate a wide range of opinions on this topic, so I'll start by giving you mine FWIW. Stapfam is correct; a lot of things affect tire performance besides width. I do have experience running 23's 25's and 28's all Continental ultra 2000 or 3000, as well as Ultra Gatorskins (28). All tires of the same width are not necessarily the same width, e.g., I put an older Continental 2000, 28 on my touring bike a few weeks ago and it is noticably narrower than the Conti Ultra Gatorskin 28 that it replaced.
I did not notice much difference between the 23's and the 25's as far as ride goes. The 25's are a little heavier so I'd expect acceleration and hill climbing to be affected some. I'm sure there was a slight difference, but I did not notice it, especially on the flat. These two tires are as close to " all things being equal" as you can get except wieght and width. The width of the 25mm might also cause some problems with brake clearance when removing the wheels.
I read somwhere (or I dreamed it) that the wider tire actually has less rolling resistance because there is less deformity and it maintains a rounder profile than the "skinny" tires. Maybe someone can either tell me I made it up or come up with a source for this theory.