125 vs 250f which one is best for my kind of riding!!?

my question is how does a 125 2 stroke stack up to a 250f four stroke, i have a cr 125 now but i plan on switching to a 250f soon but i just wanted to know maintence costs of rebuilds and that kind of stuff and what bike is best for hare scrambles...my 125 is basically bone stock and its very hard to keep up with my friends yz 250fs and my neigbors fourwheelers :/ so i thought id make a switch cause my trails are hills, mud, hills, creeks and guess what more steep hills! it starts at the bottom of this mountain and goes to the top so please help thanks!!!