RRS is popular because it's a damn fine product(a system approach), that has been around for a few years and has a very good track record. They may be a bit pricey, but their choice of materials, machining and over all build quality is hard to beat. I really think they're the bar by which the others are judged. A few years back, after I had used some of the clamping options at the time and didn't like most of them, primarily Manfrotto(due to their bulk). I looked into Kirk and liked the collar for the Nikkor 300 f/4 AFS. Then I got to see some RRS clamps & plates and made the decision to stick with one system and chose RRS.
The destination is our goal but it’s the journey that educates us. KeithR