I did many dives in both, we used to do all our winter class checkout dives there. I liked them both, something different when you're used to diving in a lake all the time. Blue Grotto used to have a deep tunnel down the back side of the over hang. There were lights pointing down into the tunnel so it was only an advanced dive but as close to a cave dive as many of us will ever come. We did an advanced class night dive in Devil's Den once, talk about black water diving. Being a sink hole not much outside light gets into the hole so at night it's absolutly pitch dark inside, only the dive lights provide some light. We'd turn off our dive lights and follow the students around in stelth mode.
I liked them both, had alot of fun diving them and would like to dive them again someday.