They are totally different systems. Bluetooth is mainly the wireless connection between the audio device (i.e. player) and the speaker(s) while the Sonos is the platform that delivers the audio in the home.
From the functionality perspective, the later has the better remote control (e.g. complete UI rather than just stop, play, FF, RW), better connection (IP-based in either wire or wireless. can be between rooms), better performance (e.g. no extra compression/decompression involved. Sync playback between multiple clients).