The overwater villa is the single most recognisable image the Maldives sells, and it's worth understanding what you're actually paying the premium for before assuming it's automatically the better room category.
What you get
Direct steps into the lagoon from your own deck, a glass floor panel in some categories, and a level of privacy a beach villa can't quite match — no one walking past your window on a path. It's also, simply, the photo most people picture when they picture the Maldives.
What you give up
Overwater villas are almost always priced above equivalent beach villas at the same resort, and depending on the island's layout, can mean a longer walk (or buggy ride) to the main restaurant and jetty. Being directly over water also means direct sun exposure with less natural shade than a beach villa's palm cover typically offers.
When a beach villa is the better call
If snorkelling the house reef is a priority, beach villas are sometimes positioned closer to the best reef access than the overwater row — worth asking specifically rather than assuming the pricier category is automatically the better located one. Beach villas are also the more practical choice for families with young children, given direct sand access instead of a lagoon-edge deck.