A few thoughts...
For the price of a piggyback attachment, you can buy a first rate progressive press designed from the ground up to be one.
The RC is compatible with Hornady's LNL press conversion kit, so that it can use the LNL bushings too, as are several other presses (Lee Classic Cast and Redding BigBoss, BigBossII & Ultramag). Other presses have different quick change systems for dies: Lee has the Breech-Lock Challenger press with their own QC bushings, and Forster Co-Ax has a snap-in/out floating die retention system.
Neither Hornady or RCBS single stage presses have very good spent primer handling. Lee Classic Cast, Redding BBII/Ultramag & Forster Co-Ax all route spent primers and debris down through the ram into a tube to a bucket or catch bottle.
IMHO, Hornady and RCBS are equivalent in quality of equipment, and both of their kits have very good selections of tools, so whichever one is available at a better price (including incentives), get it. I do generally prefer Hornady over RCBS dies though.
Andy