regarding 3 wheels vs 4, I see 4 wheels having some advantages. If you picked a tricycle configuration you'd want two wheels up front and one wheel in the back for stability. If you have steering and drive in the front, you have a more complex system that doesn't get good traction going up steep hills. If you put drive up front and steering in the back you lose good handling at speed. If you put steering up front and drive in the back, you only have one wheel drive.
From growing up on a farm, tractors with tricycle gear in the front don't work as well in the snow, and I'm not certain why this is. I think it's because you have to break three paths through the snow rather than two. In addition, a four wheel setup in snow tends to go in a straight line. If you get tricycle gear stuck in a rut, you're going sideways and it can be difficult to maintain a straight line.
From growing up on a farm, tractors with tricycle gear in the front don't work as well in the snow, and I'm not certain why this is. I think it's because you have to break three paths through the snow rather than two. In addition, a four wheel setup in snow tends to go in a straight line. If you get tricycle gear stuck in a rut, you're going sideways and it can be difficult to maintain a straight line.