Most of the above +1
I’ve got 2 and one is better than the other at somethings but not others.
1 sounds slightly better, and more reliably connects to the phone, but drops out when the car is started and the voltage drops for a second or two.
The other occasionally BT connects for calls only and needs plugging in/out to re-set the connection, it’s also looser in the socket to gets knocked more.
Aside from that they both do the job, and the sound is at least as good as the car’s FM, but that may be down to the relative loudness in the mix being played on the radio.
A jack plug might be more reliable, but then you may as well just plug the phone jack in. The upside of the BT-FM transmitter is you can skip songs/podcasts “hands free”, still needs your hands but it’s a big easy to find FFWD button, no need to pull over and unlock your phone.