I would decide on 2st or 4st first. Once you have that decided, I would buy the best one you can find within your budget. I don't think you would go wrong with any of the bikes listed.
Not sure if you're going new or used, but there's a couple decent used KTM 300's on craigslist at decent prices right now.
I don't know karate but I do know ca-razy.
'06 Husqvarna WR125