We're in territory that's extremely hard to prove. I'll just say, when your Gator has the hours/miles on it that ultrarunner's Sami has we can further discuss the repairs necessary to get you there.
As to repair parts and their cost, see above statement. You can buy a complete front axle assembly for a Sami for what you'll pay for an individual axle shaft on the Gator.
With little time investigating it is visually apparent that the chassis of the large Kubotas are built stronger and with longer lasting design than the Gators. That would be proven on the scales as well.
I'm not flaming any color. Just clarifying.
Final point, I believe ultrarunner is already $6000 ahead of you in cost output. So your Gator has a lot of catch-up to do.