I wouldn't say natural competitor. The Aeon is 2x the money so it should be better across the board. And I find that it is. Staging is way better on the Aeon and it sounds more open. There was a slight weirdness in the tone in the mids of the pm-3 that I could never overcome (possibly EQ could have fixed it, I understand that Sonarworks has a preset profile for it now). Weight and overall comfort is pretty comparable.
I'll give the nod to the pm-3 on portability. It's smaller and has a sleeker look. The Aeon for me is more transportable.
I've ordered the Aeons to replace my PM-3's as my portable set up. When I say portable what I mean is when I am not at home. Holidays, hotels etc and not taking the bus or going on a train or walking down the street. Really looking forward to early May