My cub cadet went nuts on me last year so I ended up rebuilding transmission myself. Cost me around 200 in parts and just trying to make it through this season since I have had to do bunch of work on house and replace down stairs a/c unit. Did a bunch of research on them last year and this spring. If you are looking for a tractor model it seems from what I was able to find is the Huskvarna upper end mowers are probably Best Buy for the money. Since I have 2 deep ditches and a couple of steep banks I been looking at the bigger one that has a newer heavy duty transmission. It has a automatic differential lock so if one wheel comes off the ground it automatcly puts power to other wheel. Next up is the real johndeer mowers from dealers but they are about twice the price for equivalent mower. Almost every riding mower in tractor style today is built by Murray mowers. They have different body style and paint everything else is pretty much the same. Most have a hydrostatic transmission that is about half the size as what they really need.
In zero turns that's a different animal all together. Doing my research found most home owner models are not built or designed to cut much over a acre. Light transmissions and light stamped decks. Lower end commercial models with tougher transmissions and fabricated decks are much better in longevity for the average home owner. If I bought one today it would probably be a Bad Boy mower. Next would be a Toro. Bad boy I like the way they are designed for ease of maintaince and they seem to have a pretty good track record. Built pretty heavy duty in all the critical areas.
Hope this helps just a little.