Ken70, you raise valid questions. Dillon's top of the line press also moves dies instead of cases.....is there a quality or ease of use reason? I don't know.
I did ask a R & D engineer at RCBS if he thought I'd want to replace my Rock Chucker with this new press.......he said "No." (No elaboration except that he suggested that the Rock Chucker remains RCBS's top of the line single station press.
What I am attracted to about the press is the wide open front. It just seems it will be easier & more convenient to use even for lefties. Plus the small footprint that mounts out of the way is really a plus....no one armed bandit sticking out in front of the bench.
I don't know whether it will "replace" anything, or even that I'll like it. But I would like an additional press, and with bench space limits, I think I'll be able to tuck it in and not miss the space.....again, we will see. Will also buy the short handle.
As for on-press priming....I only do that on my progressive. In fact I went to a hand priming machine 30 years ago. I expect those that prefer the on-press feature will not buy it (or the current Rock Chuckers) or they will give up and buy a hand primer or the awesome bench primer. (APS for my money)