I originally purchased Marvels to use with my iphone, android phone and laptop. I use skype for business on my laptop for several hours per day, so whatever hearing aid I chose had to support this. When I purchased the Marvels, they only could only be paired with one device at a time, which was a show-stopper for me, because it required me to reboot my laptop every time. (The single pairing issue has since been addressed by Phonak and newer versions of Windows 10 do not require rebooting when re-pairing.) I also found that the Marvels frequently disconnected from my laptop, which was very disruptive and for me it was a show-stopper.
Because of these two issues, I switched to Opn S hearing aids. These hearing aids support MFi so they connect directly to my iphone. They automatically connect to the iphone when I turn them on. They use the ConnectClip to connect to the laptop or the android phone using Bluetooth Classic and the connection to the hearing aids is Bluetooth LE. The ConnectClip is reliable (zero disconnections) and the sound quality is good. They are connected to the iphone and the ConnectClip at the same time. For me, this is very handy, because that way, I can leave them connected to both my iphone and my laptop all the time.
If you have an iphone, I recommend the Opns. The MFI connection is superior to Bluetooth Classic. If you have a Pixel 4, according to Oticon, the Opns will support ASHA with a firmware update. If you have an android phone that doesn’t support ASHA or a laptop, the Marvels might be a better choice. Of course, you should always consider which hearing aid works best for your particular needs. For my situation, I didn’t notice any difference substantive between the Marvels and the Opns, so my decision was based on connectivity.