Iggy,
From my experiences the 2 main options are the Sena units or the Eartec. Personally we chose the Eartec single ear unit. As another poster stated, I did not trust relying on a "Bluetooth" connection. I have experienced problems with device pairing with other devices and did not want to chance it with boat coms.
Our Eartec units worked flawlessly and the sound quality was very good. With the single ear, you can hear other things like marina staff on the dock, or the VHF radio if you are the pilot. If the microphone arm is lifted up, it turns the mic off so you can talk to "others" without speaking loudly in your partner's ear. The only issue, is the "slave" unit is not easy to turn off (at least know for sure it is off), so removing the batteries as a matter of use is a good idea as is the lanyard idea!!
However, they are not inexpensive, but they do work great, reducing stress, ensuring better communication between crew members, and I feel there is value in that.
We are not associated in any way with this company, only a customer.