
Some brands are more widely available (distribution/quality/price point), some brands less so. Sometimes you ride a foil that just covers almost all your wants - horses for courses. I am not brand loyal at all, just trying to ride what gives me the biggest smile (however I do appreciate a good product -
GoFoiland
Ozoneare top of my list right now). I was not familiar with Uni or SPG but from the looks of things they are very highly crafted products - you may find they are hard to beat performance wise, but it looks like your wallet could take a bashing

Maybe this answers your original question better than I could:
My Fav Unifoil Setup & Tuning Tips - with Tom Earl (youtube) @2:29 he says he prefers the 83cms over the 75