Hi,
first point is the need of 2/3 time zone functionnality, which closes the match.
Second point, spirit of both watches is not exactly the same, like their esthetic. GMT's bezel and band are little more glossy than sub's, which is more an "outside" watch.
Sub offers also choice between date or nodate, GMT don't
.
For me i prefer the no date Sub C than the 116710. For my own i have a 114060 and a 16710, which is a good couple i think. The 16710 offers the choice between 3 insert (or more !).
Good luck and choice!
