The exc is a better comparision to the GasGas as they both have the wide ratio tranny and IMHO is much better suited for eastern terrain. I've had a 99'exc and a 98' mxc and right now, after owning the 200ec, I would choose the GasGas 250xc. They make good power everywhere and turn better than the KTM. The GasGas shifts much better and has a 6 speed tranny.
I think the KTM might be put together a little better. The GG probably has better parts availability and parts are usually cheaper.
KTM 125 Enduro
I've ridden both. I'm not going to be much help, though. Both are great bikes. The GG allows you to mix and match engines and suspension which is nice if you really know what you want. In my area, KTM's are much easier to get parts for and re-sell a lot better. Jim Cook at www.smackovermotorsports.com will be able to get you any GG part you'll need, though.
For me it comes down to frame size. I'm 6'2" and 210 and the slightly smaller GG frame feels too cramped for me.
There are several (some heated) threads on this subject. I've owned KTM EXCs and now a GG XC250. They are both solid, high quality motorcycles. The GG is hand made, and parts are fit together tighter than the KTM. The KTM is designed with higher volume production (faster assembly) in mind, fits together a little cleaner, and is eaiser (faster) to work on. In some areas the KTM is detailed better, but has its minor bugs in others. Both will last way longer than a Jap bike.
From owning 2 KTMs for 2 years and the GG for almost a year now, I'd say the GG is cheaper to own after the initial investment. The few simple parts I've needed (nothing major) were much cheaper than the KTM equivalents. Availability is never a problem, either locally or ordering from Jim at SMS.
I'm with JEB, it comes down to ergonomics and comfort. I'm only 5'8'', and the GGs slightly smaller frame fits me better. My 6'4" buddy is slightly cramped on my bike, but taller foam and different bar mounts are available.
I'm in northern NJ, and the EC spec motor is great in the snot and rocks here. The GG also steers faster than the KTM. You can tune the steering response and ride height with different length pull rods, It's very flexible in set up. Stock, the XC suspension is slightly stiffer than the KTM. I had mine revalved, but nothing works great here (rocks) stock anyway.
Buy what fits you. Confidence and comfort affect performance much more than any mechanical differences. Good Luck.
I've ridden both extensively. The Gas Gas XC has stiffer suspension than both the KTM
MXC and EXC (both share the exact same suspension), so the KTM would be better suited for your eastern type conditions.
The Gas Gas also has a more violent hit in the middle of the power band than the Ktm 250, making it light up the rear wheel in the sloppy stuff.
This comparison is for box stock bikes off the show room floor with no modifications.
As one of the posts said above, if you are looking for a Gas Gas for eastern type conditions you would want the Gas Gas 250 Ec,
softer suspension, a torquey/smooth/fast motor especially designed for enduro type riding. Good Luck and Happy trails !!!