I guess, the question is what does he want to do with his new "Amiga" ?
Just play a bunch of 20 year´old games ? WinUAE,WinUAE and again WinUAE....
Use apps of that time ? Still WinUAE .....
Use it as a "modern" computer browsing the web and stuff ? MorphOS on a descent Mac is the best choice here.
Just tinker around ? AROS,FPGA or even a real C=-Amiga (not to be mistaken with the current NotC=USA-crap) is what he should want.
AmigaOSXL is really 2fold:
AmigaXL, a port of UAE for QNX both 10 years out of date.
Amithlon, a much faster emulator acting like it is a full OS, but getting it to run on 2011 HW won't be easy and it won't make full use of it (as it's also 10 years out of date).