The main differences are as follows: The Beach villas are bigger (70 sqm)and are detached, facing the lagoon side of the island. They have a daybed on the decking. The Deluxe Beach Villas (51sqm) are semi detached and are close to the sandbank.
Club 33 is one of the most exclusive experiences available through Disney. The club itself is invite-only, and it costs a pretty penny in membership fees. The reason it's so exclusive is because of Walt Disney's original vision as a place to entertain VIP guests.
If it's your first trip to the Maldives staying in an overwater villa is probably the best option. It's a major bucket list experience so it's one you don't want to miss. That being said, beach villas are in no way a second-tier option.