I'd be happy with either but got funds for only one for now and as of now, both watches are in the same $4XX range on Ebay/online sellers.
Major downside with the Tsuno chrono is unconventional lugs which limit it strictly to either bracelet or OEM leather from Citizen. I actually saw this in person today on a co-workers wrist and it's a very nice substantial piece but dial is little cluttered in my opinion but not too bad as the AR coated sapphire makes the hour/min hands stand out.
The GMT is kinda new and a JPN release so not many threads here but the standard lugs opens up to a world of 22mm rubber/leather straps easily. I know it's more of a pear VS apples comparison but which you guys prefer if you to pick one?