R1, AG tires have a very aggressive tread, or Lugs that can damage a good lawn. However, they are much better for working in soft soils and muddy areas because they provide more traction.
R4, Industrial tires are a great compromise, can be used with more confidence on lawns (in 2WD), and still provide fairly good traction.
I've used both, and am very happy with the R4s I have now.
John