Generally, the Caribbean is much better for snorkeling compared to the Pacific, so I am surprised that your experience in Cuba was poor!
Having the disappointing snorkel tour in Cuba and the option to take the Tortuga Is. tour, I would not be recommending the tour for you. Often the snorkeling can be a coin flip....we have been twice and had two different experiences, to say it is a 100% satisfactory would be a lie. The snorkeling relies on Mother Nature's day...if it is optimal, (no wind, no rain, time of the year, a sunny day) it can be perfect, but nothing is perfect as far as relying on such things!
The boat ride is beautiful! Sometimes you can see whales, dolphins, and rays leaping out of the water! Sometimes not....
There are a couple of places to snorkel off the beach: one on the north side of Santa Teresa, right at El Ray Patricio, and another at the southern-most end of the road in Mal Pais at the boundary of Cabo Blanco reserve.
What you choose to do is up to you! Remember....Costa Rica is an adventure! Enjoy your stay in our corner of the country!