Le Meridien Phuket is located in a very nice cove where no other properties are located and where beach merchants cannot go. It is not very far from streets where many things are happening. The property has buildings that are fairly well maintained, but outdated. One more positive point: the food is quite good.
On the opposite, Le Meridien Khao Lak is newer (rebuilt after the tsunami - but it was brand new, when it was destroyed) and does not have much around. Very nice beach, too.

So, it all depends if you need or not, to have a beach city nearby, with all its activities. If you don't, Khao Lak, with its newer type of hotel, is a much better choice and you can also access it from the Phuket airport.