As someone partial to Porter, Kelly, and Weinberger - I have quite a few interpretations of what I think merits a "Competitive Advantage". While some of these definitions lean more towards the complex, there is one I keep handy at all times;
‘Competitive Advantage’ is doing what the other person is not willing to do.
When we set out to build Rocketr (originally dubbed ‘Rhonda’), I spent dozens of hours in coffee shops pitching the premise to anyone that would listen. The reason? Practice. It was the single fastest way to improve the idea, thereby improving the product.
I also knew that the more I did it, the faster I’d get somewhere.