Hi vrsindous, I have been to the Marriott Vacation's Playa Andaluza and it was fantastic, an absolute haven away from the madding throngs of beach dwellers of other more basic resorts. During our time there, we left the resort onyl twice, we spent so much time enjoying the on site activities and facilities, there was little need to go elsewhere. The apartments are first rate and I would recommend it highly.
As we live in the UK, I cannot comment on travel from the US, but the drive from Malaga Airport was only about 45 minutes, so easy enough.
I've been to both the resorts in Marbella and am going back to Marbella Beach Resort in two months time (and can't wait).
To be fair there's not a lot of difference between the two as they seem to have been built in very similar styles. Personally I prefer the Beach resort over Playa Andaluza due to its location - it has many more restaurants and a better supermarket within walking distance and the beach was slightly better. Playa Andaluza is in an area that is still being developed.
Both resorts are great and a pleasure to stay at with the usual Marriott space and comfort.