Gears

Ok so I know very little about gears and was wondering how much of a difference than can really make? Like what are the different shift points between stock gears, 3:55's, 3:73's, and 4:10's? This is all for a 95 GT that im very close to buying. It also already has all the basic bolt on. Also which do you guys like the best. Tops Speeds anyone?

Sorry I just realized I put this in the 4.6 and not the 5.0 forum, but what do you guys think anyways.