I think they do make a little difference, I did notice that going to a smaller diameter arrow but keeping about the same exact weight, Ive increased a few fps. I was shooting Easton 2314s now Shooting the Easton Carbon Excel St's 400's I never had to adjust anythign on my bow which I found to be a good thing. The aluminums and carbons are shooting the same but the carbons seem to be a little more flatter and faster. Maybe its just me. I think I run each one through a chrono and see what I get.