ABI-V1 alpha release, when that's reached they will have completed something I have (in the past) doubted would ever be finished.
So yes, I would give AROS the nod as number 2 in that placement (with a real possibility of gaining number 1 position as it improves).
But as all three OS share a common base, I'm not sure its even fair to consider them as competitors, rather there branches of a common tree.
Pick your flavor and run with it.
All seem to have a promising future.
Its hard to believe there are this many options this far after the 'demise' of the Amiga.
For a 'dead' system, there sure is a lot of development going on.