Airfare to get to the west coast may change the impact on your budget of the Mexican cruise, so check that out before you decide. Also, I have heard, but don't really know that RCCL is not as great as it used to be. Others may have better input on that.
PM me if you want info on ports, etc. Been to Mexican ones a dozen times at least (I lived in L.A.) and Caribbean even more.
Have fun no matter what you choose!
IMO, the beaches and activites available in and around the western Mexico coast just aren't that great. The beaches are rocky, and water is not clear like the Caribbbean. So, based on itinerary alone, I would chose on of the Caribbean cruises.