The main difference is that Spotify is an app for private use, and Brandtrack is an app for commercial use.
In the Spotify terms & conditions you'll find that using it for commercial purposes is not permitted, and doing it might get you fined. This is because Spotify pays its licensing to record labels in a different way that Brandtrack does for commercial use, which ultimately impacts on the artists that they represent. If their music is played in private, they get a smaller percentage than the one they receive for commercial use.
The other difference between Spotify and Brandtrack is the way the app works. Spotify is built to let you configure your playlists manually because it's conceived for personal use. Brandtrack's purpose is to handle music for you so you can dedicate to your business, and to delight your customers, so you can drive more sales.
Learn more about Brandtrack's licensing.