Harry M.-
Hydros are infinitely variable speed 0-8 mph forward, 0-4 mph reverse. No high/low and not necessary in a hydro. The brakes are easy to reline with some material from McMaster-Carr.
As for gear vs. hydro, I prefer gear drives, but not for mowing or snowthrowing. I prefer gear drives for ground engaging attachments, trailers, and snow plowing. Both have their issues that have to be corrected, and they wind up costing about the same to fix if you want to do it right.