@Iggy
Do you have any particular software in mind that doesn't run and how the hell can you think that compatiblity should be higher than under emulation in winuae?
If some old software isn't working in os4, just let it be started from uae. So compatiblity is probably the best in any amigaos ever since you can run both amigaos4 exes & classic executables.
MorphOS runs 68k, PowerUP, WarpOS/WarpUP, OS4 and MorphOS binaries.
OS4 runs 68k, WarpOS/WarpUP and OS4 binaries.