I'm considering switching from R4S to RPi4. The only thing blocking me is that I can't get any SquashFS image working, on my RPi4. See below.
FriendlyElec make some great hardware, but their lack of engagement with the OpenWrt community is disappointing. I don't like that they make their own OS, but don't upstream any of their patches. I was happy with their product, until I encountered the reboot problem and was told to just run FriendlyWrt. They didn't ask for logs or anything.
RPi4 should be a much more mature platform. However, the fact that none of the SquashFS images work is troubling.
If you do end up going down the RPi path, you will need a high quality passively cooled case or actively cooled case; they run hot. The R4S is much better, in that regard.