Bill Walsh in The Score Takes Care of Itself:
Don't let anybody tell you that a big ego is a bad thing. Tiger Woods bill gates, Warren Buffett have lots of ego. And so does anyone anywhere who is dedicated to taking his or her talent as far as it will go? I've got a big ego, too. Here's what a big ego is. Pride, self-confidence self-esteem, self-assurance. Ego is a powerful and productive engine. Without a healthy ego, you've got a big problem.
Egotism is something else entirely. Egotism is an ego that's been inflated, like a hot air balloon, pumped with lots of hot air…a big ponderous entity, slow, vulnerable and easily destroyed. And
When evaluating people, I prize ego. It often translates into a fierce desire to do their best and an inner confidence that stands them in good stead when things get really tough. All the great performers have ever coached had ego to spare.
David Senra highlights a concrete demarcation between ego and egotism:
Arrogance is when you stop learning from other people.