I was faced with the same decision. Kubotas are definitely more popular, and there are more dealers around, but Bransons are going up as well. When I was looking at buying mine I had similar concerns but I called their headquarters and they are doubling their sales every year. Anything can happen to any company, but I don't see Branson going anywhere. They are backed by Kukje, who has been in this business for many years and they have major contracts with cummins, build tractors for john deere, etc.
Now that I have had my Branson a while, and after talking with others in my area who have kubotas, I get BETTER service than them. The kubota dealer in my area is one of the largest in the country. They sell a lot of tractors. They are so busy that often if your tractor needs repairs during the busy season(now) it can easily be 1-2 weeks because they are so behind. Also they sell a lot of tractors to businesses, etc that are their primo customers and if they come in for service you get pushed to the back of the list. My dealer has always been there for me. I am definitely a person and not a number to him. If I have problems, he comes to me to fix the tractor. If he can't fix it on location he will haul it in at his expense, bring me a loaner tractor if it is going to take a while, and bring me mine back once it is fixed. I guess it all boils down to the dealers in your area. I guess the way I see it is at least here Kubota acts like you owe them something and they have more than enough business and don't care about you. My Branson dealer is working hard to establish a business in a tough market with strong competitors and he is doing so by going the extra mile.
I am not knocking kubotas as I have limited experience with them, but if you are going to be doing a lot of work like you mentioned moving large rocks, stumps, etc the branson will do much better due to its weight. To me weight is everything. If you are just cutting grass it does not matter, but if you are moving heavy loads, plowing, even running a box blade in some conditions you will run into problems with a light tractor. You may have 35 hp, but what good is it if your tractor is too light and you just spin your tires?