My
BX2670 came with R-4's because "that's what they had in stock because everyone wants them" and I've hated them from day one to the present. If I had a loader and played in the dirt, I might choose differently. If fact, yes I would, I'd want agricultural lug tires!
While this is my first Kubota, I've ran various types of lug and turf tires to mow grass and do garden work for 45 years. In that time I've found ag tires work best for mowing the yard, working the garden, and general playing in the summer. The ag tires spun less than turfs, thus tore up the lawn less. In winter, swap on some turfs with chains. Rubber spins on ice if you have a real winter where the ground freezes, no matter what the tread pattern. Chains disappear between the lugs of ag tires and become virtually useless. The R-4's aren't quite as bad, but they still swallow chains to a degree which lessen their effectiveness. Not to mention they are rough riding where the chain does cross a lug.
Speaking of rough riding, good grief, those R-4's are beating me to death. Either turf or ags would give a much smoother ride because they aren't as stiff. I'm down to 5psi in the rear tires hoping for some flex, and still waiting for that flex.
Sure wish I had waited for turfs, even though the snow was piling up and I had no way to clear it. Since this is my first 4 wheel drive tractor, the lesser traction of the turfs could easily be offset by engaging the front wheels when needed.
Of course, others needs and desires will be different, but in my case, where most of time I'm mowing the yard, or pulling a subsoiler/ground breaker, dragging old fences out of the brush, and blowing snow in winter where there is frost in the ground, turfs would be the best, overall, never change, tread type. In a perfect world, I'd have ags all around in summer, and swap on different rear wheels with turfs and chains permanently mounted on them. I can swap rear wheels faster than I can install chains.
One thing haven't tried, is studs in the front tires for winter. I think R-4's would be excellent for this. Coupled with chains on turfs on the back......