Going to be honest and say it depends on what you do, what you want, and how confident you are in your mechanical abilities..
When I first started getting into the hobby and learning about the mechanical side of the tractors, I tackled narrow-frames. Simple, easy to work on --and parts are affordable and available.
Now I'm moving up. I own an 86, 169, and an 1812 --and I have to say that they're all brutes, but the 1812 is the best I've owned when it comes to operator comfort and confidence in the machine.
Now I'm on the prowl for a 982, 1572, 1872, or 2072.