First, let me say that the current crop of progressive presses being offered by Dillon, Hornady and Lee are all very good tools with excellent warranties and support. That said, following some five years of hard use, I consider the Pro 2000 to be an exceptional press and have been extremely happy with it.
I previously used both the Dillon 550 and 650 and they each worked extremely well, albeit demonstrating a need for little "piecey" parts from time-to-time. Not an issue with the 2000. My reason for the switch involved the move from loading high volume(s) of a single cartridge, (Bullseye and IDPA competition), to moderate quantities of several different cartridges with fairly frequent changeovers. For me, the 2000 is the quickest and easiest to convert of all of the current offerings, including Dillon and Hornady.
The RCBS is arguably the strongest and simplest progressive available. I prefer iron to aluminum, especially in the critical toggle assembly. The precision and ease of use of both the priming and powder metering systems, respectively, is excellent. I did purchase the optional tube priming system but haven't used it as I've enjoyed the strip system far more than I thought I would. My preference is for manual indexing over auto index. Interestingly, my rate of production did not change between the 650 and 2000; however, to be honest, I did not use (or want) a casefeeder on the former.
If I were starting over again, I would definitely choose the 2000, even for high volume match shooting. It's obvious why it was/is the press of choice of the NRA technical staff and experienced shooters and writers such as John Taffin.