This is a nearly unanswerable question, since it's based entirely on personal preferences. My recommendation is that you compare itineraries and the excursions available at the different ports and see which appeal to you more.
As for my own experience, I have done both 7-night Eastern and Western out of Port Canaveral. Here are my takes on the two:
- I enjoyed the port towns more on the Eastern (Philipsburg and San Juan) than on the Western (Grand Cayman, Costa Maya, and Cozumel)
- The excursions we did on both were great. Some things (beach, boating, snorkeling, etc) you can do on either one, but some things are very specific (hiking in the Chacchoben ruins on the Western versus hiking in the El Yunque Rainforest in Puerto Rico on the Eastern).
- Our Western had more ports of call (3 plus
Castaway Cay versus 2 plus Castaway Cay on the Eastern). On the Western, I felt like I was getting more action for the money, while I equally enjoyed the extra at-sea day to relax on the Eastern.
All in all, if I were going to do one of them again, it would probably be the Eastern, but I'm very glad to have done both.