Personally assuming the price is the same or very similar I can't see any reason not to buy a GC IV over a GC III. I know some people prefer the older GC I and II as the overall build quality and materials are supposed to be better. For me the big selling point of the GC IV is the flush pocket lips, although there has been some issues with ball spitting because of this. (They can spin around in an empty pocket and pop back out.) I think they have a better leveling system too.
Personally I think the most important factor other than the table itself is the table mechanic who sets it up. A bad table mechanic can make almost any table look and play bad and vice versa.
And BTW I have a
very similar looking table made by AMF years ago in black with gold corner castings. I love the color combination even though my table is pretty well worn. (The gold finish has worn off the top pocket castings for example) Note that the rails are a matt finish now, if they were originally glossy the varnish has long since worn off. I think the Brunswick black GC tables are a gloss finish and if so I'd imagine you'd spend a large amount of your life wiping the finger marks off them.