The tank can carry a bigger gun, but that's about it. Most of it is armor that it has to haul for 100-300 miles at a time (before it runs out of fuel).

Also, lol at "Ukrainian tractors". Their biggest (only?) tractor plant was destroyed in Kharkiv. Most of their tractors are... John Deere. Probably why they got so good at modifying them that Americans are buying their software :D