It appears top be a luck of the draw in either case.
For me the Quectel firmware was very stable whereas the OSS firmware wasn't. "Stable" as in it would periodically crash, but would come back on its own within a minute. The OSS firmware would also crash but would usually not come back until a reboot.
This was with v0.5.5 IIRC. It seems to have gotten better since the 0.6.x versions of the OSS firmware.
Really the bigger reason to switch to the OSS firmware is that there's a privilege escalation vulnerability in the Quectel firmware that IIRC they still haven't fixed. In any case even if they fixed it in a new firmware release you wouldn't hear about it to know you should install it, whereas the OSS firmware is now being distributed through fwupd so it could be almost as mindless as updating your distro.
It‘s not just the Modem Firmware, it’s also how the distribution manages the modem. I am mostly using DanctNIX (Arch Linux ARM) to test apps for [0], but also have postmarketOS stable installed (on eMMC) as a backup for when I need "phone things" to just work - postmarketOS stable is very good at that.
I no longer use the Pinephone because of the aforementioned issues, however at that time, I'm pretty sure I was at the latest and greatest firmware version available (which one that specifically was opensource or proprietary, I can't remember).
The experience was so horrid, I just quit using it all together and never looked back. But maybe if things have improved, I should give it a shot again.
For me the Quectel firmware was very stable whereas the OSS firmware wasn't. "Stable" as in it would periodically crash, but would come back on its own within a minute. The OSS firmware would also crash but would usually not come back until a reboot.
This was with v0.5.5 IIRC. It seems to have gotten better since the 0.6.x versions of the OSS firmware.
Really the bigger reason to switch to the OSS firmware is that there's a privilege escalation vulnerability in the Quectel firmware that IIRC they still haven't fixed. In any case even if they fixed it in a new firmware release you wouldn't hear about it to know you should install it, whereas the OSS firmware is now being distributed through fwupd so it could be almost as mindless as updating your distro.