My favorite distro is of course "Aros Vision" :-)
I think all distros are different and it all depends where you want to use it. On X86 there are the most distributions, on ARM there is only aeros (based on Broadway X), Broadway X is certainly more targetting Linux. AspireOS is for Netbooks/Notebooks, Icaros for heavy desktops (generally). And Aros Vision is targetting 68k (real hardware and emulation, for real hardware I want to create a more lightweight version in near future).