Reps are getting scary good these days. I dont think they will ever be exact, cause they really only have to be "close enough" to get the job done. However they have made leaps and bounds in the way of improvements.
Of course you can never replicate a $8-10K USD watch for $300, and that will always show through. I think reps have their place and I love all of mine. There is always the pride of ownership and inherent value in the genuine article. That goes double in regards to Rolex, Patek , IWC etc. You can pretty much get within 15-20% of the book value of those brands, anywhere in the world at anytime should the unfortunate need arise. Rolex of course could probably be sold in a mud hut in the middle of nowhere, being perhaps the best known watch, and one of the best known brands of any product in the world.
Congrats on your GMT II. Beautiful watches, they have really got my attention as of late. I LOVE the all gold with the green face, amazing timepiece, but I feel the stainless is a much better choice for daily use. Wear it well!