Not sure why they haven’t reviewed them yet. Perhaps they are too inexpensive to bother? In any case, I think the one they would choose is this one:
1. Bluetooth version 4.0 (4.0 means lower energy use in mobile device)
2. APT-X / APTX
3. 3-year satisfaction guaranteed warranty
4. 4.4/5.0 Amazon reviews rating
5. Reasonable price
Buying a separate Bluetooth receiver for your existing stereo or radio is a much better approach then buying a completely new one, just to get a built-in bluetooth receiver.
Beware. This is for a home audio system, not a car. That would be a separate review.