I've seen BDD advocates say "BDD is just TDD done right." (e.g. here and here) They seem to be saying "It's important to write your unit tests at the appropriate level of abstraction, using language from the problem domain, phrased for a human reader. Domain experts (e.g. users, business analysts) should be able to read, and perhaps write the tests."
More recently, I've seen "TDD is just BDD done right." (e.g. here and here) These people seem to be saying "It's important to use your unit tests to drive the design of your code. BDD is missing that important action." I think they're noticing that BDD doesn't include a Red-Green-Refactor cycle.
I think they're both right. Striving to write tests for humans provides the best guidance for refactoring, carrying the Ubiquitous Language deep in to the system and improving DRY and Cohesion in the system.