I believe I've owned the bike you're talking about, so here's my experiences;
A long time ago, in a galaxy far, far away, Honda made two ranges of dirt bikes, XR and XL. The XR were competition bikes and the XL were street bikes. Just about everything was different between the two ranges, although the engines tended to be developed from the same basic configuration. The XR were more powerful, but had higher seats and lacked road kit. Whereas the XL were lower, slower, but road legal.
The thing is, in this galaxy far far away (Japan) most people bought the street legal version, but longed for the extra power and speed of the competition bikes. So a bright engineer thought of putting the XR engine into an XL frame, and the XRL/XLR was born!
So a couple of years ago I too saw a XR250L for sale at a good price. So I whopped some knobblies and hand guards on it, and it was fantastic. As an introduction to green laning and getting muddy it was brilliant. It's light enough to pull out of a ditch, and fast enough to get you from green lane to green lane before nightfall. I sold it to a mate of mine as his first dirt bike, and he's converted now as well.
Okay, now the downsides,
* It makes very little power, as in 'less than my lawnmower'. Coming from the CRM it will feel sooooo slow.
* It will also feel really really heavy, because compared to a CRM it is heavy.
* Next is the suspension, which is street oriented and would need serious work to make it enduro ready. After a couple of months of ownership I found that I was starting to bottom the suspension out. As my confidence grew so my speed over the ground increased, to the point the suspension couldn't keep up. And I'm not a fast rider.
* Finally it's got a RFVC head, where the camshafts run directly in the head, i.e without bearings. If the previous owner hasn't been too liberal with the oil you might have wear problems with the head. It is possible to have bearings retrofitted, but it's not cheap.
My advice is to stick with the CRM250 for enduros. Whether a 4 stroke is better than a 2 stroke is a debate that could go on for years. In my opinion it's down to personal preference, and if you've been riding 2 stroke for a while then I would stick with it. Really if you want to go 4 stroke you should be thinking of the 400cc class, which with modern bikes is a step up in power whilst keeping the weight close to that of the CRM.
I personally went up to an XR400, which has good suspension and enough power for me at this point. I prefer air cooled bikes because I'm learning and that means I crash a lot. I'm sure I'd have gone through a lot of radiators by now with a water cooled bike. Also the XR400 engine is mature and has built a reputation for being reliable. I have thought about using the XR for overland trips, but the fuel consumption isn't too great. We'll see.
Hope that helps.
'02 Honda Africa Twin
'00 Honda XR400