I was recently in Vegas and went to both properties. We had booked in at Encore via Amx FHR and as we were coming in from the East early in the AM our Strip view room was not available so for a small charge they upgraded us to a Salon suite at the Wynn. Well over 1500 sq. ft. and simply unbelievable. The private entrance and lobby is well worth while not to mention the service.
As far as Mirage, I had previously stayed at a Penthouse back in the days under Steve, but seeing today the entrance and inside of the place is generally looking tired and worn out I would pass on that. I will say, LOVE is a wonderful show and we enjoyed it much and would go back in a heartbeat.
Stay at the best you can and visit the others as time permits.
There is no doubt there are so many choices to choose from in Vegas and each has it's price points and amenity's. You can book several days and check out early and go somewhere else if you do not like it till you find something that fits.
For me, the Salon suite personal Message room is over the Top for a Hotel room. I'm ready to go back....