I'd say a KX80 because I rode one and it had lots of power from bottom to top, no need for fanning the clutch and i am 150lbs! Suspension was great, very plush, never bottomed out. Breaks were v.good. I felt very in controll and confident on the bike. My friend has a YZ80 and i have to clutch it like hell to get it into the very narrow power band,suspension is OK,not as good as the KX, the brakes felt just as good as the KX, I fekt more in controll on the KX than the YZ because it had more bottom end and it was easier to ride. The KX has a powervalve but the YZ doesn't. I cant comment on the other 80's but i have heard that the RM has been greatly improved after a long time, is is like the KX, i dont think that the CR has a powervalve but i have heard that it doesnt have much bottom end. You need bottom end to get the bike into the powerband quicker and it is easier to ride faster with bottom end and your clutch will last longer! My personall opinion would be the KX.