From my perspective, the dealing with loss of registration on head movement is not really an issue. I plan out my work location and set things up so I don't have to move the head up or down during the process. This also includes using such things as an ER collett "extension" so I can use short tools such as a center drill as well as the longer drills etc that I put in colletts. And while some people think having a lighter machine is better, weight is your friend and translates into rigidity. No the RF31 is not particularly rigid, but I am sure it beats the heck out of a 0704 type of machine.
Just my .02 worth (and that ain't much after inflation:})