Lots of good advice here. Some of it is conflicting, which indicates to me that different tractors and ground conditions can yield different results, or at least different impressions of the results.
I am one who uses R-1s (just happened to come with the tractor). No tread is perfect for all conditions, but my advice is don't sell R-1s short. I use them for everything including mowing. They do imprint the grass at times, but the grass springs back in a short time. The extra traction, when needed, more than makes up for any drawbacks, in my opinion.
I agree with Walrus' post above. He and Rat are the only two I know of that have used both R-1s and R-4s and have felt inclined to post a strong opinion. In the Re: 4210 or 4310? thread in JD buying/pricing, Rat expresses his preference for R-1s over R-4s. I was hoping he would expound a bit more, as I too am trying to learn..., but, in any case, I have not been disappointed in my R-1s.
OkieG