I stayed at the Encore which is annexed to the Wynn resort. At the time it was the latest addition to the LV strip. The rooms and its amenities were fantastic.
I suggest you choose the newest hotel as you are almost guaranteed to have a nice luxurious rooms. Hotels don’t tend to invest a lot in the rooms; so a lot of them of their rooms and facilities look quite used and tired. I have also stayed previously stayed at the MGM and the Imperial Palace as well.