It all depends upon your dealer support. In my area, it is Gravely. However, I didn't choose Gravely solely for this reason. I run all Gravely turf mowing equipment due to it being the best equipment for my particular requirements.
I have a 2000 54" Bunton (same as bobcat) walk behind. Parts cost is on the high side. But you can get around that if you buy from www.j-thomas.com But I have been pretty happy with the mower. My .02 cents.