I like AROS. It's very impressive, and open source, and really nice, and the price is unbeatable....
... but it doesn't feel like the Amiga to me, and its API is a lot closer to OS3 than OS4, but that will only affect you if you code. Plus with an AmigaOS 4 machine you know it's not going to have compatibility problems.
Interesting, feels like Amiga to me.
Also I don't think AROS emulates a 68k for OS3 apps yet, does it? JanusUAE is great, but not suitable for simple commandline tools and stuff.
AmigaOS 4 feels like home. 'nuff said.
Seamless UAE (with JIT) has been integrated since what, 2012 or was it 2011? OS4 has it's share of issues (extremely expensive hardware for one), but if he is interested in AROS, he should go download (for free no less) a live ISO from
http://icarosdesktop.org/ and give it a spin and see for himself if he likes it or not. Yes, there is "limited" number of video (mostly nVidia) accelerated drivers and NIC drivers, but the hardware is common and dirt cheap. He can even run it in hosted if he wants. There is no reason for him not to go download the Icaros ISO and give it a try and see for himself if it feels like an Amiga.
Think there is still AROS hardware being sold if he has to have a brand new machine that has AROS drivers for all of it's onboard hardware.