The Royal Islander is not as upscale as the Aruba Surf Club. The only Royal Resort that would compare would be the Royal Haciendas, the newest of the Royals.
The Cancun Royal Resorts are well-maintained and nice, and are known for their service-oriented employees. But they are not as fancy as the newer Marriotts. In Cancun, the Royal Sands would probably be the most elegant, but it does not have granite counters in the kitchen, for example.
The Royal Haciendas is very new (one phase is still under construction) and has all the bells & whistles. The drawback to this resort is that it is located in an undeveloped area north of Playa del Carmen. In time, there will be a golf course near by, along with shopping and restaurants. For the time being, there is a free shuttle provided by the Royal Haciendas to/from Playa del Carmen, but it ends at 6:00 pm, so a taxi ($10) would be needed to return to the resort later in the evening. It is a beautiful resort with nice pools and beach.
In Cancun, there is a great public bus system that will take you anywhere, easily, for about 65 cents per person per ride. The advantage to Cancun is that many restaurants, clubs, and shopping are just a bus ride away.
We have never been to the Omni, so can't comment on that resort.
If you adjust your expectations and go to the Royal Islander not anticipating the upscale decorating of the Surf Club, you will probably enjoy your trip. Most exchangers are very satisfied with their stay. The pool is not as extensive, no lazy river, no jacuzzi, but it is not nearly as crowded as the Surf Club either.
Here is the Royal Islander web page with information on the villas, resort and a photo gallery:
http://www.royalresorts.com/the-royal-islander.asp
Another new timeshare resort that recently opened in Cancun is the Westin Lagunamar. I don't know about the difficulty of exchanging into that resort since it is so new.
You can read reviews of all these resorts at
www.tripadvisor.com