I'm not going to say the Vegas ones are "not worth it," but my experience in Paris was better, both in terms of food and service (at L'Atelier St. Germain). The execution at my last meal at L'Atelier in Vegas was not bad but slightly flawed - it's maybe close to a low-mid 1* Michelin, in my opinion. They could be fairly good options if you want that kind of food when in Vegas, and there's far too many other places in Paris for me to visit that I probably wouldn't return to the Paris branch anytime soon. Although, I think Twist is an even more interesting option in Vegas. Never been to Gagnaire Paris, though.