#1 Hardcore wrestling
Anyone who watched AEW's inaugural show entitled 'Double or Nothing' knows that it will be a lot more 'hardcore' than WWE's PG product. If the abundance of blood during the Dustin vs. Cody match wasn't enough to convince you, the brawl between Moxley and Omega through the crowd certainly should.
Jon Moxley came up through the independents and was known for his hardcore style of wrestling. Unfortunately, this side of his personality had to be curbed during his WWE days because of the company's family-friendly policy.
But not only does Moxley now have a whole lot of hardcore specialists like Jimmy Havoc and Joey Janela to work with, but he can also actually take part in some brutal matches. AEW does not seem to be as geared towards kids as the current WWE product is, I believe.
Jon Moxley could potentially thrive in such an environment and showcase his true skill-set.