will qualify my comment with the fact that I stayed at the Zilara Rose Hall when it first opened and really wasn't all that ready to be open in some aspects.

Which has better dining options and/or beverages if there is a difference there?

Rose Hill wins the food and drink war, hands down (especially if you are staying at the Zilara vs the Ziva. This isn’t to say that there is anything bad about the options in Cancun, but Rose Hall is several steps above it (and most all inclusives for that matter.

Beach quality? Long walkable sand or rocky and inaccessible beyond the property? Water temps, clarity, fun waves?

Cancun's beach and water quality is far superior to Jamaica's at these resorts. While Jamaica's is more secluded, as the beach is technically public in Mexico, the sand, water and swimability can't compare to Cancun.

Pools

I'd say this is probably a draw between the two resorts.

It is hard to say about the other points, they can really vary day-to-day.

Overall, if you just want to stay in the resort walls and enjoy what you paid for (drinks, food and sunshine), go to Rose Hall. If you want the ability to go outside the resort and plan to spend a ton of time on the beach and in the water, go to Cancun. (Cancun also has a really good coffee shop).