I've used the Leupold standard dovetail rings in the past on a R700 270 and it seems to work fine. I was considering the Leupold 1 pc dovetail, but then started looking at the PIcatinny/Weaver style for more real estate.
I've looked at Warne, TPS, Farrell. They all range in that $112-130 price range, but is what makes them different?