How old is your son? This is an important factor when considering facilities for children. Both kids clubs are excellent, there is very little between them. One thing to bear in mind is proximity to the kids club, at Playa it is situated in the central building behind the restaurant. As parents you can be sat close by around the pools or be quite close in your villa. At Son Antem the kids club is in the main clubhouse which is close if you're at the pool or restaurant but it could be some distance depending on where your villa is. At Playa there is a dedicated kids pool for younger children which has a small slide and splash area, it also has a lifeguard. There is another pool where watersports are played which would be suitable for older children and then a further pool for general use. My youngest (9) prefers Playa because of the kids pool.
Son Antem has the main pool which is heated and a large unheated pool on the hotel side that MVCI guests can use. In addition there are a number of unheated pools that are shared between villas. They are a bit on the chilly side in May/June but by summer they are great. I've yet to find one that has been overrun and quite often I can be the only one using one, particularly for an early morning swim. If you have a villa situated adjacent to the pool it is very convenient although one of these pools is never more than a minutes walk away.
A car will be a necessity at Son Antem particularly as you'll want to go grocery shopping (relying on the Marketplace is too restrictive and expensive). At Playa it depends on whether you want to go exploring or not.
I prefer Son Antem as I like the villa's and the pools. I also prefer the island to the mainland and the airport is much closer than that at Playa. Playa is just as nice, it simply has another feel about it, more compact and inclusive.
