Much agreed, I was renting a couple (4 or 5) of years ago typical size of ski I would rent was 170-175,  when I bought my first pair I bought a pair of 186 mojo 90's which was a big step up, my first time on them I was thinking on the chair how much harder they would be to turn etc.....all the things that would come to mind.  Anyway all those thoughts went away after like 2 laps, bigger skis = better for just about everything (exception urban).  I am assuming you are a kid and have 155 or 160 park skis?  If you move up to something like a 171 or even 176 you won't notice that much of a difference especially if you center mount them.  Powder, All mountain, big mountain etc .......lengths is a long discussion that I don't feel like having.