I think a lot can be said, but I will just add this: I respectfully think you are wrong about "influence". One should consider what influence is. Are we talking about their influence on other musicians or on the general public or fan base? If it is the latter, then yes, Amy Winehouse has a greater impact, if it is the former, I believe the "jazz legends" have the edge.
I meant influence on the record buying public. I agree with what you said.
Take my words with a grain of salt. I want to work in the music business so I can really appreciate music that sells well. I think Amy is different than a lot of pop music (I hate a lot of it) in that she has a fresh sound that most pop doesn't. As a musician I can also appreciate the "good" music.. but also see it as most of the times not worth the (pardon the dated term) vinyl it's pressed on, commercially speaking.
I like Amy because she's a good balance between commercially successful and musically fresh.
