There's also the fact that in AEW, he's basically THE guy. In WWE, he'll be A guy. He'll most likely play second fiddle to Roman, Seth, Cody, and whoever strikes Vince or HHH's fancy that particular month.
In fact, I'd go so far as to say that in WWE, he'd most likely be jobbing out a LOT, because they do that with popular guys, because "oh, they can eat lots of pins, they'll get their heat back."