It goes either way.... comparing stock to stock is apple and oranges. to get a rb25 to what a rb26 can do with just a boost controller kind of evens out the price point.
If you get into pistons rods and head work start out with a cheaper rb25 as with comparable mods I have seen rb25s put down some serious number's. but lets understand that neither are cheap.
I know this is an rb thread and I bleed RB, but I have said it many times. if it ever fails catastrophically I'm going GM 4.8 with twin 76s