I have stayed three times at Pier 66, and now always walk to the beach instead of staying at the pool. It gets very crowded in season and has too many trees for my liking. Also feels very scruffy to me.
Coral gables pool is a suntrap, and is quite nice to spend a few hours by, but by no means a resort pool.
However i would go for Pier 66 as i prefer the Ft. Lauderdale area and Las Olas to the Miracle Mile.
Galleria Mall is much improved lately and is a nice walk along the beach 30-45 mins, Sawgrass Mills and Aventura Mall are easy drives. Bal Harbour is also not too much further on from Aventura.
If you stay at the pier 66 beg, plead, bribe whatever, for a tower room i found a big difference between them and the lanai rooms and it made a big difference to our enjoyment of the hotel.