A big consideration is where you ride. If it's technical XC, then the 19" will become more than you can handle, and at the worst time - typically around a sharp turn with a some roots and a big pointy rock on the other side. If you don't have to turn quickly, bunnyhop, ride steeps or do anything overtly difficult, then go for the larger frame. Perhaps a cyclocross bike is more up your alley?
