> it looks a 7448 is the better option.

Yes, and not surprisingly. After all, it's the most advanced G4 CPU ever built (as long as we don't count the lower clocked but better integrated SoC G4 CPUs that is).

> Are there any incompatibilities reported with it (if I recall the
> 7448 support was experimental).

None that I know of. I suggest to ask Ruud as he's the only MorphOS user with a 7448 that I'm aware of. As you can see (and as Jim already mentioned here in this thread) Ruud has reported rather low memtest results for his 7448 equipped Quicksilver 2002 machine:

https://morph.zone/modules/newbb_plus/viewtopic.php?forum=11&topic_id=7474&start=28