If I hadn't been in such a hurry[for no reason],to get this tractor home,I woulda told them to put r1's on mine.
But,[this is my first experience with r4's on a farm type tractor],after using them for a while now,I think,for me,they are best tire.
It depends on what your using your tractor for,conditions,etc.
Like I have said,there are advantages too both.
Just like a turf tire,if you were mowing yards or golf courses and maybe clearing your drive of a little snow,than they probably would be your best choice.
r1's with out a doubt provide better traction in mud and deeper snow.
R4's are tougher[well],are wider for better stability and if loaded,really help in this. Don't leave as deep a ruts as ags in places you don't want ruts.
On ice,ag's you would think would be the worst of the three[without chains],and with chains all three would probably be about equal,but the wider ones might be better there.
Just depends on what your using your tractor for,mainly.