Had a Rockchucker for the last 40 yrs, like it a lot, primer disposal is its only main fault, now, they have the Rebel to take care of that. Had a Co-Ax for about 9 yrs now, there was one thing I knew it wouldn't do going in, when I bought it, hazards of universal jaws, always a limitaion on anything "universal". That cartridge wouldn't work with their shellholder adaptor either. I was surprised, even though I likely shouldn't have been, that rim thickness can be an issue, doesn't matter if u use new or old style jaws.. Was thinking of adding the curved linkages, they make sense, but, aren't really necessary. I think that the die mount setup is still far superior to an FA, so are the jaws, and the QC. No beefs with it really.
That said, I just picked up a MEC Marksman to try out, liked the floating shellholder, primer disposal to start with, and I thought MEC had enough experience at building a press to make sure it was a good one. And I am not at all disappointed with it, they did it right, it is really smooth to operate. I doubt if anyone would at all be disappointed with one. Certainly smoother than the old Rockchucker is.
If you have the patience to wait for a Co-Ax though, go for it, you'll be happy.