One thing I love about Cory as Betta tank mates is they spend most of their time out of the Betta's territory. IMO, this allows the Betta to get used to activity without it being constantly in its face.
But the real reason is I find Cory to be clownish with their behavior. I'm glad you're enjoying them as much as I do.
Great photos, too! Now to get some of your Betta looking at them like they're idiots.