They all are good places. If I were staying in San Pedro and choosing among those four, I would pick Banana Beach for value, friendliness of staff and being on a good beach.
But, like Sunset Beach, Banana Beach is really not within an easy walk of town. It's about 1 1/2 to 1 3/4 miles from town, and Sunset Beach is maybe 1/2 miles farther south. There are some restaurants within walking distance, esp. of Banana Beach.
Mayan Princess does not have a pool.
So that pretty much leaves you with Fountain Blue, which is new, nice though with fairly small suites and a bit pricey in-season if they stick with their rack rates.
That's my opinion only -- yours may vary.
Belize books and publications by Lan Sluder:
Belize First Magazine (http://www.belizefirst.com
Fodor's Belize & Guatemala Guide
Belize First Guide to Mainland Belize
Adapter Kit: Belize (the first and only comprehensive guide to living, retiring, working and investing in Belize -- a best-seller on Amazon.com)
UpClose Central America
San Pedro Cool (coming soon)