I have to ask, why do you not like the GC4, and what is it you like about the earlier III over the IV?
Sorry for not getting back sooner on this, just saw it. Anyway, little things really that probably wouldn't matter to anyone else. For the most part tables here in Japan have the ball return rather than drop pockets. I've yet to see a GCIV with the ball return where the balls don't occasionally roll into the drop box and then out onto the floor. This problem is so bad that, again, I've yet to see a GCIV here that the owner hasn't installed something in there to block the balls from bouncing out of the drop box.
The GCIV is also notorious for balls going into the side pocket, flipping over the rail underneath the table and dropping onto the floor. I honestly can't think of a time where I haven't seen that happen at least once a night when I'm at the pool hall.
The GCIV is poorly designed as far as their return system goes.
I like that Brunswick took the hint from Diamond and lowered the pocket liners but I gotta give them a thumbs down for keeping it that cheap plastic garbage that they've always used. The GCIV would look so rich if those liners were leather around the pocket opening.
As for playability, in my personal opinion the GCIII plays softer than the IV. I feel like the cushions are a bit stiffer. I have nothing to prove this, just a personal feeling.
MULLY