You really didn't give much info on your riding experience. Some dirt, my uncle, ninja 300.
What I would want to know is how you rode the dirt, and how you rode the 300? Were you very careful, cautious, timid? Get the 600. Were you stunting, killing it, picking up chicks? Get the 1000. Either choice you are in for a world of trouble if you ride aggressively anywhere else but a straight line with no traffic!
Get the 636 dude. Once you learn how to WOT that, you'll be much better prepared to pickup a zx10r 2016 or newer and not kill yourself, or for that matter anyone else!