First, is it honestly "one or the other"?
If you can get one now and pick up the other later I'd say go with the 390 first just because it's LE and will probably get more expensive as time goes by, especially after the last few trickle out of the boutiques and it becomes unobtanium. So now is a good time to get one IMO. The 372 should be available at or even below list price into the foreseeable future, so you can likely get one later at cost or even less maybe. Heck, if it's really a regular production model you should be able to just order one from a boutique and get it pretty easily.
But, if it's really one or the other... get the 372 unless
your wrist is really small.
But honestly, I've worn both and my opinion is... 390 is really nice, but 372 is must-have. The only reason to not get a 372 is if you really have tiny wrists and just won't enjoy a watch that size. For my money the 372 is absolutely the king of the hill, with the exception of a couple of specific vintage pieces that will probably never be available to mortals anyways
If plexi is wrong, I don't want to be right.