From the East End, Tortuga is good. And the East End is very good. But from where you are, you don't want to go there every day.
While diving off the West / SMB is better than a lot of places in the Caribbean, it's the worst diving in Grand Cayman. If you're a reasonably-experienced diver, with a buddy, and you don't need your hand held, and you're only diving in the morning, and you have a car, THEN I recommend Cayman Marine Lab. CML goes to the north wall most of the time, and otherwise the south sound if the weather demands it. Wherever you end up going, it's always reasonably close (10-20 minutes) from where you're staying.
Tom (the owner) is entertaining, has a PhD in marine biology, and you'll get to see a lot of lionfish die. My impression is that CML has its diehard fans, and you'll either love it or hate it. (I love it.)
Otherwise, Red Sail is fine.