I'm a recent buyer of a competing product, a Kioti DS3510. My property is in the Sierra Nevada foothills, and has some steep grades that I need to mow. My research here led me to believe that weight matters more than just about any other factor - the more a tractor weighs, the better it will perform as far as limiting wheel spin, which is especially problematic on grades. My 1984 21hp 2000lb 4wd Mitsubishi couldn't come close to the tops of several grades on my property, and the pucker factor running that tall, narrow tractor with my homebuilt ROPS was pretty high. When the 5' brush cutter proved too much for it, we decided a new tractor was in the cards.
Every dealer I spoke to that was familiar with the terrain in question recommended a non-HST tractor - even if they didn't have one to sell. The closest Mahindra dealer, while a very personable and accommodating fellow, was new to the tractor business. He did not have and could not locate either a 3016 Shuttle nor a 3616 Shuttle. He had no service, contracted out his service work, and couldn't get me what I wanted - so he was out.
I shopped around based on what owners said online - Kubota, Kioti, and Case all seemed to have good reputations. Most forum posters agreed that there are lots of good machines on the market, but good dealers matter more that the color of the paint. The Case dealer actually endorsed Kioti - his parents bought one new 25 years ago, and still haven't had a problem with it. The Kioti dealer has been in the tractor business 75 years, and offered to bring up a new Kioti and let me demo it for the weekend, no strings attached. He hunted up a dealer trade for a new DS3510 (which is still a Tier3) and made he a great deal. It was less expensive than a comparably-equipped Kubota, Case, or Mahindra, and when the service department saw where it was going, they filled all four tires.
I have now mowed all the slopes that I could not do before. The most extreme ones have required 1st gear and diff lock, but it made it without issue. I've run up hills, down hills, and ever cross hills on some of the moderate slopes. On the really steep ones, straight up and down, and in both orientations. With the loader, 5' rotary cutter, and ballasted tires, I'm close to 4800lbs on R4 tires. I spun out a couple of times in steep, loose soil, but was able to back down a bit then engage the diff lock and finish the climb/mow.
Had I not had such a density of trees, I might have gone to a larger tractor. I'm glad I didn't, as I avoided Tier4 and can go several places that the 45hp model could not. The Kioti tractor weighs a bit more than the Mahindra, but I suspect the gap narrows when you add respective FELs. I may add wheel weights on the rears, and about 4 5gal buckets of sand in the loader, if I have to tackle another steep overgrown hillside, but I think it will be fine otherwise.
Good luck with your search.