I am on my fourth new Gator and now have the XUV. I know it was totally overloaded but I had it filled with 3/4 rock road pack to where it was heaped in the center and running off the sides. I'm sure it was nearly a ton of rock. It is also rated to pull like 1500 pounds. I can pull over 200 bushel of corn with a total load of over 13,000 pounds and that is on grass not rock or pavement. I am a firm believer in the JD quality and stamina. The RT 900 will do what you need it for but the XUV has a fun side as well with it being a lot better on the trail, faster speed and acceleration, more nimble, true 4 wheel drive for the mud and snow, etc. The RT 900 is a workhorse, the XUV is both a workhorse and a sportier machine.
Another thing to consider is the ergonomics of both machines. I looked at the Kubota pretty hard before I bought but I am a big person and had a hard time getting on and off because of how those handles and seat guards are in the way on the drivers side. I get on a off a lot and that was very important to me. There is also more leg room on the Gator with more comfortable seats. Nothing big to some but things I looked at other than just how much it can hold or how much it weighs.