Amithlon = linux 2.4 + something
Amiga OS XL = QNX + something
By the way, Amithlon still run fine,
I've tested it with a Fujitsu-Siemens laptop.
Openpci and AHI drivers are still developed for it.
Actualy, UAE (E-uae) is faster on my box (mainly due to use of vesa drivers with amithlon). When I use Abrowse with Amithlon, I never use the up and down keys or I have to wait some secs till the end of scrolling.
Anyway, neither Amithlon or AmigaosXL supports AGA or Paula.
If you want to play old games, you need UAE.
As both Amithlon and XL are not FULL OS, UAE is more suitable and is easily integrated with you current OS.