Welcome to FT....I see you're new so I'll warn you that you will soon be blasted to use the search feature. Problem is, it never seems to work for more than one word searches anyway.
I can't speak for the JW, but I've stayed at the Suites hotel. It's about 3 blocks off of the strip, near the convention center and close to the monorail (that takes you to the south side of the strip). There are no real upgrades in this hotel as all the rooms are the same - when I stayed as a gold (paid reserveration using a heavily discounted rate - ENTertainment I believe, but need the card) I got top floor, corner room. Thought it was an upgrade until I asked.
I still didn't complain as I think it's a very nice facility. No concierge lounge, but free breakfast every morning - either buffet or from the menu.
I would hope that the JW is nicer only cause they're supposed to be...but I know nothing about it. There's also a Rennassaince near the monoral station (as well as a Courtyard and a Residence Inn) all within a stones throw of the Marriott Suites.
Hope this helps!
-Mike