I've done most of my Akumal diving with Dive Adventures out of Half Moon Bay, but when they aren't going out (HMB can be too windy some days while Akumal Bay is still ok), or after a hurricane when they weren't reopened, I have dives with Dive Center too. My only issue with Dive Center is their DM is quick to poke, prod and grab coral and marine life to show stuff to divers. That's something I really don't like.
I don't stay at Akumal Beach Resort, but from what I've heard from people who've used Venta Diving and then Dive Center, they just about all stick with Dive Center. Venta also sends their divers to Dive Center if they don't have enough people to take their own boat out.
Have you dived in Akumal before? If not, go into it with low expectations. Even just a few years ago it was still pretty good by Caribbean standards. Now, unfortunately, land-based issues and the lack of a marine protected area have really taken their toll on the middle and outer reefs there. There's more dying, diseased and macro algal covered coral then healthy stuff. Not much in the way of adult marine life left either.
But it's still a dive, right? You do still see turtles, rays, squid, lobster and eels with some regularity. Just go slow and spend time really looking around in all the little hidden spots around coral and there's still stuff to see. Just don't expect to drop down and be wowed by color and marine life. One thing I will always love about Akumal is the very interesting topography of the reef structure.