From what I recall from my lumber sales experience years ago, the only difference between marine ply and exterior ply-(and also interior ply) was that it had a garanteed no void
core. Which means there are no hollow spots within the core veneers. As far as I know the glue used was the same. Actually, according to my most recent supplier, even the newer interior plywoods have exterior glue. Your choice may depend on what you're using it for. Just remember, if you put enough epoxy and varnish on a peanut butter-jelly sandwich, it will still stand up to the elements. But if you require the most in a construction/structural project, choose, buy and build accordingly.
You also may want to peruse this for specs/apps. Caution, it's a bit wordy. Good luck...........