Hmm, I'm assuming you want a two stroke?
Either XC or XCW. Then SX or YZ 250.
Point is, just grab a bike to ride, but don't sink yourself into any particular one. The first year it won't make that much difference, and then you will be knowledgeable for what you need/want. Then you can start dishing out the cash.
You've already proven to be a discerning fellow simply by limiting your choice to the 250. Stay away from that gawd-aweful 300.
The MX bikes will get you around on your trails and you will have a ton of fun and learn a lot but when you get serious they will start to beat you up. The suspension is too harsh and the power delivery does two things, makes it harder to hang on for long periods of riding and makes finding traction harder (this is a by-product of the suspension as well).
If you can go new, you can't go wrong with either the XC or XCW. Both are excellent out of the box and you will know that anything that gives you grief on the trail is your fault not the bike's!
16 and up 250 XCFs (one caveat, the 16 had 4CS forks that were "troublesome")
15 and up YZ250FX (one caveat, tall!!!!)
11 250 XC. Excellent excellent bike (12-16 were ok, with suspension issues)
17 and up 250XC
06 and up YZ250, excellent machines. Bullet proof. Ubiquitous parts etc. (One caveat it's an MX bike, but there are a few things you can do to help you out)