I guess I can answer this from experience, @petermo.
I first tried the OPN 1’s with the ConnectClip. I liked the sound quality of the OPNs, but I had a lot of issues with feedback, no matter how many dome and setting adjustments my AuD made.
I am currently trialing the Marvel M90-R. First off, they are a lot larger than the OPNs behind my ear due to the lithium-ion battery. However, I don’t have the feedback issues with the Marvels. I’ve had to try several domes to find a comfortable fit, and I think I’ve settled on the new small open domes that are made for Marvel. However, open domes do cut down bass tones for me.
In terms of sound quality, this is subjective, as everyone hears differently and has different perspectives as to what “sounds better.” But I have to say I think I like the sound quality of the OPNs better. Everything seemed a little more clear and crisp, and directionality seemed a little better to me. I found the sound quality using the ConnectClip during phone calls and streaming to be more solid and dependable when compared to the Marvel’s built-in mics. I think the connectivity range was better with the ConnectClip as well. If I walk too far away from the phone, the Marvels get static and don’t want to hold the connection. I didn’t have that issue with the ConnectClip. I’m also noticing when Autosense 3.0 switches settings…there is a pause or a momentary “cut-out” and then the sound comes back. I am going to ask to have Autosense shut off to see if that helps.
If I could have gotten the feedback issues under control with OPN, I probably would have stayed with them. It is also nice not to have to wear an accessory device to connect to my Android phone, but I honestly didn’t mind the ConnectClip around my neck too much. The ability to use the Clip as a discreet remote control was convenient.
OPN sounded a little more “tinny” unless I used closed or power domes, which were more occlusive and uncomfortable to me. Marvel sounds just a little less crisp on the high frequencies to me–even after REM adjustments, but that’s just my opinion.
I hope this helps.