We did 10 dives at Akumal on one trip and decided it wasn't worth the vacation time or money to ocean dive there again. Been back to Half Moon Bay many times since, just skipped the diving.
It has already been mentioned that from December to March the conditions are pretty much the same. Pick a week and you will have a great time in Akumal.
Couple tips, the transfers from CUN are expensive to the point that it is almost cheaper to rent a car (dead heat on a four night stay). Also, eating in Akumal is super expensive for what you get. You can either take out a second mortgage and shop at the Super Chomax or stop in PDC at Mega, Walmart, Chedr.....
Our LDS had a spring break trip to Coz this March. That means a lot of new/inexperienced divers, none of whom had a problem with the current or dive profiles. Get your friend a refresher and she will do just fine in Coz.
When we go to PA, we use Cancun Valet for transport. I think it's something like $150 (or less) roundtrip for an exclusive van. Also, we rent a condo when we are there, and do a lot of our own cooking. There's a pretty new Chedraui right across the highway from the front entrance to PA, which makes it really convenient, plus there's a Farmer's Market on Saturdays and Wednesdays inside the compound for fresh produce.
And I'll ditto TSandM's endorsement of the ocean diving at PA, we love it because its easy and healthy. Maybe you should rethink Akumal?