I use a KX 250. Mine is a '99 and I race D22 and UORRA (Gusse's) Hare Scrambles. Mods are MX tech valving and straight rate springs, 7 oz. Steahly flywheel, 3.5 gallon IMS tank, 1 mm shorter pull rods (raise rear end), WER steering damper and WBrothers Ti bars with bark busters. If I did it over again, I would add a small skid plate and a carbon fiber pipe guard and get the smaller 3.0 gal IMS tank, but that is all.
Pros are the excellent low end and mid range power, hard to stall motor (even stock), light clutch feel, easy starting, good reliablity and suspension that is not exactly plush, but not wallowy.
Cons are the lack of nimbleness in tight woods (even after raising the rear and running the forks lower), the vibration (minor, but pretty high for a 250), the missing magical 6th gear, the seat (or lack thereof - I've seen thicker, better padded feminine hygine products...) and radiator shrouds that catch your knees and make them sore.
I would try the Yamaha if I wasn't getting a Gas Gas. The 2002 sounds like the real deal. Both brands have made great motors for off road for many years now - good low end and mid range response. What kind of dealers do you have in your area, that reason keeps me coming back to certain brands.
If you like quick handling, try a Suzuki. I rode my friends 97 or 98 back when it was new and they really are quick turning and twitchy. You might like that, I didn't.
I'm 6'1" and 170 lbs (without gear on). BTW, my buddies KTM400exc is much plusher than my KX, but it is a little heavier feeling. The KX motor puts smiles on all my friends that ride it.