We were at the Grand in late May and did all our diving with Dive Palancar. We are going back at the end of Novemenber.
We had no complaints and had a great time. For us, the pace and style was just what we were looking for. They have a pretty set schedule - deep and shallow dive in the morning and a deep and shallow dive in the afternoon.
On Monday/Wednesday/Friday they have a twilight and a night dive.
You can do any of the dives you wish, i.e. if you only want to do the morning shallow dive, not a problem. If you are only doing one of the pair, they will come and get you, or drop you back off, respectively. You are not more than a 10 minute boat ride from the dive sites. In order to be able to stick to their scheduled times, the dives are fairly regimented - I recall the deep dives being limited to 35 minutes and the shallow to 45 minutes. The staff we encountered were very good to us.
You will typically have to book your dives the day before to make sure. We never saw more than 10 people on a boat. You will be asked to show your card when you first arrive. They offer a 10 tank package that seemed like a pretty good way to go.
The shore dive off the Grand is at most 17 feet or there abouts. Okay for getting your weights set up. Good snorkeling.
I cannot compare the operation to any others. All I can say is we had a great time, the staff was friendly and were fun to be with, and our expectations were met and exceeded.
I forgot to mention. In a lot of cases, the DM's provided the folks on the boat with suggestions (based on conditons), and let us decide where we'd like to go. They also took into account any concerns we had.