of the 3 brands we sell at the shop, we sell the most yamaha kids quads. next would be polaris then honda. the yfm 80s are really reliable, and will run pretty good with a grown man on one. the predator 90s run pretty well also, and look cool too. i built a trx 90 today and wasnt impressed it was pull start while the others are electric. the yami 80 is a 3 speed semi- manual. the honda is a 4 speed semi-manual, and the pred is auto, but it has reverse which is a nice touch. the pred is also a two stroke, and its got somewhat of a market for hop up parts from what i hear. the other two are 4 strokes.
good luck with yer choosin.