I personally think all three are excellent choices.
(Actually, Caribbean Villas is not technically a condotel, as it is a privately owned hotel, but it does have suites and apartments and in many ways is similar to a condotel; indeed, another property, a condotel, on the island has a very similar architectural design and layout.)
Similarities: All three seem to be well-managed, with friendly, helpful on-site people. All three have nice units. Banana Beach is newest, so its units are in some ways spiffier, but it has only one-bedroom units.
None of them has a restaurant, but all are within walking distance of restaurants. The Palms is closest to the most restaurants, bars, shops.
Location is one. Banana Beach is 1 1/2 to 1 1 3/4 miles south of town (depends on how you measure and who is measuring) whereas The Palms is right at the south edge of town. Caribbean Villas is sorta in-between.
Banana Beach and The Palms have pools. Caribbean Villas doesn't.
As to beach, I'd say Banana Banana Beach and then Caribbean Villas have the edge, though The Palms is near a good town beach. The Lalas at Caribbean Villas have done a little mini snorkeling area at their pier.
Grounds: Caribbean Villas wins by a mile, as it enjoys a small but lush natural setting, a mini bird sanctuary.
Belize First Magazine http://www.turq.com/belizefirst/
Fodor's Belize & Guatemala Guide