It somewhat depends on who you're exchanging through and what your preferences might be.
Polo Towers, Marriott and HGVC all have relatively high standards and good locations. Polo Towers is a little more basic in unit amenities while HGVC and Marriott are a little more plush. HGVC is slightly off strip with it's Flamingo location but still right in the middle of all the action and steps away from the Flamingo hotel/casino. Polo Towers is directly across the street from City Center, just south of Planet Hollywood and north of MGM. Marriott is also slightly off strip but very close to Planet Hollywood. HGVC's Las Vegas Strip location is further north and not really that close to any hotel/casino but, it's more of a resort with greater amenities like a nicer pool area, deli/convenience store and pool bar/restaurant. There's also Elera/Westgate Planet Hollywood, which is a resort in transition after Westgate lost/sold the management contract and HGVC took over. Great location but I'm not sure about the units or even who manages what. Eventually Elera through HGVC is a timeshare where I'd like to stay but I think we'll wait for the dust to settle a little bit more.
Then there are some off strip resorts that are maybe a little larger and have more of a timeshare resort feel to them. There's the Wyndham resort that's a couple of blocks off strip, Tahiti Village that's south of the airport and Grandview, with is maybe 5 miles south of Mandalay Bay but within walking distance of South Point casino. All are reported to be very nice resorts (haven't stayed at any personally) and are larger than the "on Strip" locations. They have more land, are more spread out and I believe have nicer pools.
Cancun and the Worldmark resorts that are south of the strip probably fit into the same catagory as Tahiti Village, Wyndham and Grandview but I have very little information on either of those two.
Cliff's at Peace Canyon is quite a distance from all the action. Tahiti, Desert Paradise and Club De Soliel are in more or less residential neighborhoods but have nice units and a more apartment complex feel to them (we've toured but never have stayed in them). Desert Paradise has changed ownership at least three times (Epic to Sunterra to DRI)
Our personal preferences are colored by the fact we own within the Marriott, HGVC an DRI systems. When we go to Vegas, we'll stay within one of those systems. I'm not certain my personal recommendations would carry a lot of weight as we are biased. Then again, there's a reason we own what we own.
Last trip, we were in the Suite's at Polo Towers. Next trip we'll be at the HGVC Las Vegas Strip location. There are a lot of good choices. It just depends on what you're looking for in a resort and you're level of comfort.