If you go hydrostatic, the dry vs wet brake is a non issue as the brakes will go virtually unused. Wetbrakes have longer life, stay cool and tend to be more consistent. I personnally don't think its nearly as big a deal as folks make it out to be, but then, I just don't use brakes all that much anyway.
My neighbor has the 790. He likes it fine, but after using other tractors, he understands why it is the economy model. To me., the platform is way to small. The loader and 3 pt hitch lever actually interfere with each other. The loader does not do simaltaneous functions. The exhaust should be routed down and out of ones face, for some reason his is a pretty smelly running diesel. This was mentioned months ago by JohnnyDeere. Nothing wrong overall with the 790, it's definitely got a place for the budget minded. The TC 30 just has more options that I would definitely desire. Once the 14 LA loader comes out with what I would suspect to be better specs then its current loader, it will be a great little tractor. Rat...