I have a gen master ultra thin pwr res and a gen Master chrono a friend of mine had a $700ish+ Master chrono rep and if they didn't have different straps I wouldn't be able to tell the difference. However, his rep ultra thin wasn't what either of us hoped for primarily because making the rep that thin probably isn't easy and likely isn't in high demand.
Point is I would suggest skipping the ultra thin versions unless you find one with alot of reviews. This was a few years ago though and my sample size is literally two watches but thats my experience. GL