I used a Rockchucker for about 15 years before I bought a Co-ax. They are solid and work well.
The Co-ax is like a Cadillac. The only way to prime on a Co-ax is to put in one primer at a time. It's slow, but primer depth is very consistent.
I bought a Summit on a whim. It's interesting in that you don't have to mount it on the edge of a bench, but the method of capturing spent primers when set up like that is pretty hokey. It has no priming system.
If you want a Co-ax and can't afford new, buy a used one.
If you don't want to hand prime or if a primer system is important buy the RC.
If you want to be able to set up the press anywhere get a Summit.