Which town to stay in is, of course, a personal choice. Dominical is the largest and has tons of hostels, bars, and packed beaches. Uvita is located below Dominical and boasts private beaches and a less touristy atmosphere. Ojochal is the furthest south and the smallest of the three towns. Stay here if you like your trips quiet and isolated.
I had the opportunity to stay in three hotels while in the Costa Ballena area. All were fantastic but unique in their own way. Oxygen Jungle Villas, located in the mountains, is a high-end, secluded resort that is best for honeymooners or anyone seeking a romantic getaway. El Castillo, located near the beaches of Ojochal, is a perfect for those looking for luxurious accommodations and some R&R. La Cusinga is located on a huge nature reserve and includes private trails and beaches for a low price. The cabins of La Cusinga are perfect for families or anyone looking for a more rustic experience.
