Although Picard and Crusher work well as friends and fellow officers, I think the characters are just too similar for good romantic chemistry.
Nathan Fillion's character Richard Castle said it best,
"Yin Yang is harmony. Yin Yin is the name of a panda."
That's why I prefer Picard with Vash. Vash's brazenness complements Picard's more sedate personality perfectly creating a very compelling dynamic to their relationship. That kind of dynamic just isn't present between Picard and Crusher.