I bought a GS after doing some research on both the Wright and the GS. Both should be quality units, but I heard cut quality is much better on the GS. I have been pretty happy with mine.
As far as hill stability, it seems great. Gets great traction for the most part, although most of the time I stay on mine because it seems to do better with some weight over the tires. In walk behind mode, it just doesn't seem to grab and wants to slide a bit more.
Also about the front coming up, I've never had any issue with that unless I accidentally pop a wheelie while trying to cruise on a crap yard with some rain coming. I'm 6 ft 225 lbs so I'm not exactly a featherweight. If you are 300 lbs, you're probably wanting to sit down on your ztr anyway
so maybe check out something else.
Overall, I've been pretty happy with my GS. One last note, I was surprised by how much better it runs once I got past the break in period. 50-60 hrs. Cuts better too.