For your anniversary, hardly anything could be more romantic than one of the seaside villa rooms at the Cancun Caribe, which you should get on a Diamond upgrade, especially during a slow week in January. The beach is quite pleasant and the very large, multi-sectioned pool is also a winner. I will warn you that the restaurant is not very good and you should be looking elsewhere for dinner. The breakfasts are OK, with very good service, and you will get a breakfast coupon if the RC is not open (as it occasionally is not).
The Westin Regina, on the other hand, is fairly workmanlike and has no rooms that I would call outstanding. The pools are not spectacular, and if I recall, one of them loses the sun in the PM, and we did not find the beach very appealing (I don't remember why). However, it does have a quite nice Royal Beach Club lounge, the restaurant is quite OK, and it is far, far away from the downtown tumult.
Happy anniversary.