I started with Kubota back in 2000. As far as i know it is the only manufacturer that makes their own complete tractor. Though now I believe you could add the Yanmar brand, TYM, and Mahindras 00 series and maybe a couple of others in Mahindras line. You can go to tractor data website and it list where what was made. The mistake I made when I bought my L3010 was getting the Glide Shift Tranny. Just did not work out for me with all the hills I have. I then went to a Kioti LK3054. Had to rebuild the engine after I got it, long story, but it was really easy to work on and turned out to be a great tractor. Medium framed and weighed the same as the Kubota L series. Dummy me wound up selling it to buy a Bobcat 227 HST(a painted white Kioti 225 I believe). Worst tractor of the bunch due to the fact the pressure relief valve was set so low I could not pull a hair out of a biscuit. Blah, blah real estate story and I wound up tractorless. Recently bought a Mahindra 3325. So far very impressed but irrelevant to this thread. But my uncle bought a 4530 last year and it is a tank. No problems, heavy built and very impressive. And I may be wrong but I believe 100% Mahindra made.
As far as problems and opinions, typically the Kioti brand has had dealership issues but I think that may be past. They usually weigh more than the other big three but Mahindra typically weighs more than Kioti. Something to consider if yard work is to be done. Right now if I had to buy new it would come down to number one, dealer support, then features I need and price. If I lived near a RK the TYM would be on my radar as well. If it was a Mahindra or Kioti I don't think you would go wrong with either. Or Yanmar for that matter since they make a engines and some complete tractors for Deere.