I stay at the LAS Marriott when in Vegas. All the rooms are suites. They were renovated in the last couple of years, as was the lobby area. They don't have an exec lounge, but you get full buffet breakfast as G/P. The staff are some of the nicest in the Marriott system. It's just as easy to Uber/taxi to the strip from the Marriott as it is from the Ren. The Ren is on the south side of the convention center & the Marriott the north side.

If you want strip & Cosmo isn't available, then Grand Chateau is your best option. If you're willing to go off-strip, I'd pick the Marriott.

Cheers.