Cleat release-which direction do you?

[Kalidurga]

Heels out. It's not a large movement, and it's quick, and you're turning at the ankle much more than at the knee.

Exactly. I've accidentally unclipped a few times with an inward twist when I've been flexing my feet while riding, but it's much more awkward and I've hit my heel on my chainring. Plus, moving your heel out also initiates an outward movement of the leg, prepping you to reach down for a stop.