Start with the sound and the size. Think about the music you and your guests will actually dance to, then look at the line-up: a four or five-piece can sound full, while larger bands with brass and extra vocals bring a bigger stage presence. Listen to the video and audio clips on each profile, and check whether the band can cover the styles you want across the night.
Three practical things to confirm with any band: whether they provide a DJ or playlist between sets and after they finish, how much space and power they need on the night, and whether they can learn your first dance. Good bands get booked 12 to 18 months ahead for peak dates, so enquire early once you have your venue and date.