Forgive me. I may be taking the wrong approach to this, but – for me – it all depends upon what kind of food I want . . . and budget.
One of the finest (and most reasonably priced) wine lists in all of Las Vegas is at Lotus of Siam (east of the Strip, on Sahara). Truly. But if no one want to eat Thai food (even though LoS is recognized far and wide as one of the finest Thai restaurants in the US), then have a great wine list won’t do your husband, or his client, any good.
The wine list at Jaleo (inside the Cosmopolitan) is excellent, but a) mostly Spanish; and b) if no one wants tapas and Spanish food . . . also, it’s rather noisy. Presuming your husband wants to communicate with his client, this wouldn’t be a good choice. However, José Andres has another place at the SLS – Bazaar Meat – which we enjoy a lot and they have an excellent wine list which is much more broadly based (that is, wines from all over the world, not just Spain).
Scarpetta at the Cosmopolitan, Carnevino in the Palazzo, Julian Serrano and Sage at the Aria, Craftsteak at the MGM, and virtually every other steak house on the Strip will have very good to excellent wine lists.
But – again – it depends upon budget.
OFF the strip, your husband should check out Marche Bacchus, a French bistro and retail wine shop where everything in the store can be served in the restaurant. In Tivoli Village,
If he is out in Summerlin, he should check out T-Bones Chophouse at the Red Rock Casino-Resort-Spa.