While I feel for you and Spydrlk, this makes two noted HST issues. A search of TBN with multiple search words, really did not bring up much.
So, although you had an issue, it does not indicate a reliability problem overall. I saw posts that indicated folks did not understand HST, some had issues with them centering and a few other minor issues mostly fixed by regular maintenance. This place has had millions of posts, but not many at all that indicate actual HST failures.
So, reliability does not seem to be an issue with either tranny type; hydraulic or gear.
I in no way want to downplay the fact that you and Spydrlk had issues; I would be upset if one of my tranny's had an issue. But, overall, I do not see the reliability issues. Not here. I mean, we're talking 0.00001% reliability issue.
I have driven a bunch of different tractor; mostly for homeowner stuff, and backhoe work. My old Farmall-A was easy to use with it's antique gear tranny. A friend had a 30hp Massey CUT with a shuttle shift(had to clutch to shift, start/stop). Easy to drive. Spent fair time a Kubota
L35 GST. Like that tranny, although did not drive a lot; was using the hoe. So, not downplaying gear tractors...
I personally, would probably go gear for a plowing tractor. Like that guy on TV, RonCo, "set it and forget it". Set the tranny in gear, and plow.
Our 2001 Kubota has already suffered an HST failure where the directional control would not return to "N" and transitioning from F to R or vice-versa was an excersize in wheel stands and skidding because the control valve was sticking. This all eventhough the suggested maintenance has been preformed exactly as specified by Kubota. I'm not making degrading remarks toward the Mfg, just stating facts.