Generally, I prefer r GMT, but not in gold. I personally don't understand the fascination with gold. I think smaller, understated dress watches are fine with a gold case, but MUST have a leather strap. But big, chunky, clunky sport watches like the GMT Master, to me, just look like one is trying way too hard to show that one is loaded.
As to your dilemma, get the day-date, if you have the budget for it. Wish it wasn't in rose gold, personally think that looks more feminine, but I'd completely prefer it in stainless, but that's me.
I think they're telling you they don't want to work on it. What kind of terrible corrosion could a 12 year watch have that it needs a freakin' new case? I have a Seiko 7002 diver that's twice as old, has been serviced by the previous owner, and it have no corrosion and the case looks perfectly fine. I think I'd find a different watchmaker to do the service on the movement.
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