Bacardi is commonly used for coquito because it's easy to find and cheap to buy. It’s a great option, especially if you're making a coquito for the first time.
Don Q Cristal is a rum that is easy to get your hands on. It won’t strongly impact the drink's flavor while still providing the necessary booze to make it a real coquito.
Rum Zacapa gets distilled using the Solera system, which is a method of aging. In general, aged rum will elevate flavors of vanilla, cinnamon, and oak in a coquito.
Brugal Añejo is characterized by sweet notes of caramel, brown sugar, and toffee that, alongside notes of vanilla and clove, channel the flavor of fresh baked goods.
Venezuela's Diplomatico rum is a rich addition to your holiday coquito. Diplomatico has several types of rum, and which you use comes down to preference.
If you prefer to use a clear rum, Diplomatico Planas is a good option. For something aged and a bit more interesting, Diplomatico Rum Reserva Exclusiva can mix things up.