It's actually a Sea Dweller, not a GMT or Sub. In any case, I
think Omega's a lot more commercialised than Rolex, and something
like a Patek would never survive the way I wear watches, so I stick
with Rolex as a tough and reasonably respectable brand.
That said, the black-and-white dial chrono is a Tudor 79170. I got
that instead of a Daytona because it's got a date window and a
rotatble bezel, which I find much more useful than the daytona's
techymetric scale.