I heard somewhere that oakleys have the least distortion of of any goggle. They shine a light through the front of the lens then have a sensor behind it and they can tell any distortions that would happen in the corners of the lens etc. However, thats from a purely optical standpoint. You should go try on some goggles at a shop and see which ones fit your face better and have a tint you like better. I/Os do come with an extra lens, and are much easier to change lenses. However, when I went to the shop, crowbars just fit me perfectly. They felt better on my nose even than splices. But thats just my face shape. cheers.
ps. Splices and crowbars are made for bigger faces than i/os, so if you have a super big head you might want to look into oakleys. and splices have a wider field of vision than crowbars. but its all preferance.