Certainly possible we could have differing experiences here. I would say that on my drive, which approaches a 25% gradient in one spot and averages 12% over most of its length, I have had a challenging time even getting up it to plow down. There is no way any of my machines could have plowed up it. I have tried it all, ballasted, unballasted, bucket, blade, etc., without substantial improvement in any circumstance. My tractors would plow decent when flat, but we do not have much flat around here. The other safety issue I have here is that these tires slide also and when they do they let go quickly and without much warning. These tractors are heavy and they tend to not want to slow or stop when sliding. I have slid each one of my machines over the years to the bottom of my drive and that is not fun. Thankfully no equipment damage or personal injury, but these occurrences caused me to get a plow for my Gator and use it as my plowing machine. It is faster and does better anyway. My opinion is that the R4 tires are simply too hard to get good traction in snow. They have absolutely no give in the sidewall or tread. This is compounded when they are liquid ballasted and it's cold. As one responder mentioned a snow-specific tread compound or more malleable tire for winter may be a better option given the weight of these machines. The best tractor I ever had for plowing was my little X series 595. It would plow and climb anything without chains and was an awesome little snow mover. It had the HDAP tires on it (also known as 'peanut' tires) and man, what a machine. It made all the big machines seem pitiful by comparison. I probably would have kept it but it would not power a loader very well given its limited hydraulics and thusly was not a good tractor for my then overall needs.
John M