If I were in the (happy) position of being able to chose between them I'd take the GC IV. The rails are all the same width (The Metro has these odd rails that taper into the corners) and if you are into competitive play the GC is the standard model used in a huge number of tournaments.
Assuming you have the budget for a new high-end table like a Metro you may also want to check out some other options, like Diamond and Gabriels tables. Personally if I wanted a Brunswick table and had the budget and desire for something other than a GC I'd go with a Gibson because I love that Centennial/Anniversary design, and just maybe the Manhatten because it is pretty original looking.