Buy a dual sport KTM 500 EXC or Husky FE501 an then you can ride anywhere. The big CCs sound intimidating but the design puts out very linear power and nice torque. The driveline is very robust as most of the time you won't be stressing it much.
I already have a dual sport. I want something smaller and lighter.
Oh ok although the 500 EXC is not really a dual sport. It is a dirt bike that can handle a motocross track with a few lights hanging off of it, very handy for linking OHV trails. At 240 lbs dry The 500 is probably about 50lbs lighter than your 250L with fluids.
If dirt only then I lean towards two stroke and my first choice would be a fuel injected KTM 300 XC-W TPI or the Husky equivalent. The 300 power is full of torque. A rider to be lazy and not have to constantly shift. With the fuel injection it will pull easily if you end up in too high of a gear on a technical section. So easy to ride. If you are racing then you may want to go smaller but if not the 300 is the gentlemen's two stroke. At 223lbs it is pretty light.
I have always had a 300 stablemate to my big bore 4 strokes. I had a 2004 with over 500 hours on that I absolutely rode and raced the crap out of. It is still running and on many original components. My current 2009 has been trouble free and soon there will be a 300 TPI taking it's place.
There is nothing wrong with Betas but KTM/Husky hold their value so well that they are less risky. The landscape is littered with oddball Euro bikes that hung around for awhile and then disappeared. My buddy had a 250 TM that he couldn't give away even though it was only a few years old.
Whatever you choose, don't choose boring!