I didn't stay at the villas, but I saw them. Right now Westin is constructing about 36 more of them to add to the dozen or so they have existing. The villas are smaller than suites, but have their own splash pool and from what I can tell, all face the ocean. Plus side is the increased privacy you get with these, minus side is that they are set apart on the more secluded section of the resort, and thus are not right in the main action areas of the hotel (IE, pools, bars, restaurants). They are nearer to the spa and rec center, however. The beach area where the villas are seem rarely used, so you would also get the bonus of increased beach privacy, if you are looking for that. I didn't see any on the inside, but I wouldn't say that they were architecturally unique, if that is what you are looking for. Basically, they looked like little houses built to match the architectural style of the hotel.

I believe there are also some services that you would only be able to get at a villa, such as a private outdoor massage or chef-attended meal. (You can still get an outdoor massage, at the beach, however)

Personally, I would book an oceanview suite over a villa, unless I really wanted the splash pool or if I wanted the extra privacy. That's just me, though.