personally if you have owned the motor for while and have had good luck with it I dont see what your accomplishing by switching to a 225. You could probably switch reeds and get you prop worked and run just as good.
Going from a 2.5 to a 3 liter..that 3 liter has a lot more grunt down low, and should carry a bigger prop on the top end. Worth about 3-5 mph on most boats.