I have four of the RCBS universal hand priming tools, two of the tray models and two of the APS strip models. I have tools dedicated for large and small primers so I do not have to change them. While I do not have the RCBS shell holder model, but I have a Lee Auto Prime (round tray model) and the bench top RCBS priming tool that uses shell holders.
I find the universal shell holder model much more convenient to use for the most part. You do not have to go scrounging for the shell holder to use with the priming tool. I do not know if the trays are interchangeable between the two styles of RCBS hand priming tools.
There are a few cases that do not work with the Universal shell holders, 25 ACP and brass .410 shot shell hulls are two that I have found so far. Also, occasionally when a primer is not lined up with the primer pocket, the case gets launched across the room if you apply too much pressure. This seems to happen most with 45 Colt cases for me.