I would stay away from the VTS system. Like stated earlier, they're pricey and also complex. I know someone with a Case 95XT that burned up 3 hydraulic pumps in less than a year after running those. Evidently, they are heavy to spin and once you get them packed with mud it really works that drivetrain.
As far as track machines vs skid steers, it all depends on how you will be using them. If your running on dirt/sand/mud 90% of the time, track machines IMO are the way to go. It's not just for traction. They are less bouncy, they grade better, float better, and push better than skid steers. If you're on and off pavement, running on debris, or traction isn't a concern, then skid steers are the way to go. It really just comes down to what your using it for.
I prefer a vertical lift machine because I work in tight places sometimes, and they're also better for loading trucks. I don't know that a radius lift is any stonger than the vertical. I've pushed and dug with each and they both seem as strong as the other. Just my $0.2.