I've owned them all except the RZ. The Pentax 67II, the last incarnation of the venerable line, was the nicest to hold and lightest. Unfortunately I didn't own it but got my hands on it when a bunch of us met up in Miami. At the time I was shooting an RB that got sold because it weighed the same as my 4x5. If one were to do any landscape stuff at all the 67II would be my pick. In the 645 format the Pentax NII was highly liked. If your intending it to be studio bound a RZ or RB is fine. The camera I would not shoot in a studio would be a 6x6.