"Caravan" definitely. I know some people would be fine never hearing it again. I'm not one of those people.
If I ever hosted a jazz radio program, I'd call it Jazz Caravan, and "Caravan" would be the show's theme music (of course). More specifically, Duke's 1937 version would always be the program opener, and the closing music would always feature someone else's reading of the song, a different interpretation every time.
I love "Perdido" too -- as a Clark Terry-ophile, disliking it is not an option. But I don't love it nearly as much as I love "Caravan."
Cootie Williams with Duke before he left Ellington to join Benny Goodman?
or
Cootie Williams with Duke after he returned in the early 60s?