I just changed out my clincher warm up wheels from 23's to 25's. I used Vittoria tires, rated for a max of 145psi. I definitely don't feel any difference as far as flex in the turns with the wider tire. They are mounted on fairly narrow rims, too. If my race wheels had wider rims, I'd go with 25's on them. BTW, I weigh around 185lbs.
Hope this helps,
PI