I would argue the EarPods fell out of your ear because of the cord. That's what I almost always found if the EarPod fell out of my ear -- not so much fell as pulled out by the force of the cord twisting against it.
That said, I have never had an issue with the most recent generation of EarPods. They have only come out of my ears when the cord gets tangled on something. So I am hopeful. Really hoping they are good for many activities, though as long as they are OK in the gym for the machines or workouts, it covers most of the activity I need for them their.
So I've been playing with mine for a day now...