For a beginner, a 4 stroke will be much easier to ride. They make a lot more low end torque, and you don't have to rev them as hard to make power like you do a 2 stroke. 2 strokes can be fun because of the powerband, but if you're not used to it, or trying to learn, as soon as the bike comes on pipe and starts making power, you'll get thrown off it if you aren't expecting it. They're really not great for beginners. And anybody who says that 2 strokes make good low end power have either never ridden a 4 stroke, or have been riding CR500's or something. You can't even compare them to the low end power of a 4 stroke.
Not to mention, almost all the good 2 strokes left out there are motocrossers, which are loud (annoy neighbors and are likely to get the cops called on you if you're riding on public land), usually lack a built in kickstand, and require frequent maintenance.
A two stroke is certainly easier to work on, but it requires maintenance more often. A 4 stroke is a little harder to work on, but requires maintenance much less frequently.
And while yes, two strokes have largely gone by the wayside with regards to motocross, the reason they don't make any more 2 stroke trailbikes is due to emissions and noise. The US has restrictions on all that these days. (especially in CA!)
I would strongly recommend going for a 4 stroke trail bike anywhere between 200 and 400cc's, depending on how tall you are and how much you weigh. An enduro bike like a CRF250x, or a Kawasaki KLX300 might fit the bill for you.
They've both got lights, have a kickstand, make reasonable power without being scary, and are 4 stroke, have electric start (not really necessary, but they just happen to have it) and both are reasonably quiet and easy to maintain.
Other bikes to look at would be something like a Suzuki DR300, (DR200 if you really don't want that much power and want a lightweight bike) a Honda CRF150 and CRF230, or maybe an older XR200. The Yamaha WR250 looks pretty good too, although I have no personal experience with them. I would steer away from a TTR 225. Ridden a couple of them and they weren't particularly high on power and were HEAVY!
Anyway. Thats just my 2 cents. I've been riding since I got my first bike when I was 6 years old, and currently own 26 different motorcycles; its a great hobby, just ride safe, and be sure you have the proper gear to go with your new bike! (I'm assuming you probably already do since you rode 4 wheelers before this)