I have done both. At GC, stingrays are everywhere. So are people, although usually separated in groups. You are in about waist deep water. I've done this three times. We just went to Gibbs Caye a month ago and it was more on a beach. We saw just a few stingrays, but did interact with one. Mostly the guide held it. It did feel a little more free at Grand Cayman with so many.
We were just there last week and they were both up and operational