Both. Here is an example of his draftsmanship skill..
"Stan Lee showed me Ayers' splash page for a Daredevil and asked me, 'What would you do with this page?' I showed him on a tracing paper what I would do, and then he asked me to do a drawing of Daredevil the way I would do it. I did a big drawing of Daredevil ... just a big, tracing-paper drawing of Daredevil swinging. And Stan loved it."
So not just personality. His layout skills were impeccable and just outright better then anyone around at that time.