I'm similar in build to you, only difference is I prefer the track and have a long (too long to admit) history of MX. As my sig says, I have a RM250 and my son has an 06 250F, when I get off my RM to ride the 250F it is a VERY noticable drop in power. I would never consider that drop in power. The 250f is easy, fun and all the other things you hear about, but it does not have the power my 250 has and there are too many times I want or need that power.
Since you have the two stroke 250, I would look at 4 stroke. However, if you truly are just a woods rider I really don't think you will like it the first time you are an hour in and the bike stalls or dies for whatever reason and you kill yourself trying to restart.
Four strokes are fun and easy, but don't believe all the hype. They are NOT the be all end all the press and mfg's want you to think they are.