Scale and mindshare, more data, and the ability to operate with slimmer margins, or to operate at a loss in any local market long enough to muscle out competition- which they already do.
Uber has the same kinds of advantages that Google, Amazon, Facebook and Starbucks have in their respective domains.
Existing taxi industry got upended by Lyft, which then got upended by UberX. I think the value of mindshare is overestimated, and most consumers will happily jump the ship for whatever is more convenient.
Scale is a competitive advantage in homogeneous markets. But even if you're the most efficient ride facilitator on the streets of New York, this does very little to someone looking for a ride in Des Moines or San Sebastian.
Uber has the same kinds of advantages that Google, Amazon, Facebook and Starbucks have in their respective domains.