I had used the old style Jayhawk mini mill from1998 until last summer when I purchased a Jayhawk Pro Jig from proshopguy on BR here.
I had absolutely no problems with the jig...I just wanted something that I could leave the ball locked into the jig and still swivel it to install a slug or something.
Innovative an Jayhawk both make quality products and it seems to me that the basic jigs from both companies are much closer to being the same than they were when I opened up my pro shop. Personal preference is going to play the biggest decision here.
I want to upgrade to a mill with digital readouts in the future but for now the Pro Jig is going to have to do.
Best of luck with your decision.
Doug's Pro Shop
RotoGrip Star Pro Shop
Turbo XTreme Dealer