I've always thought of it something like this:
Rock music (including indie, post punk and such like) - Music for the brain. Lots of emphasis on the lyrics providing food for thought and so on. Also sometimes resulting in clever widdley solos. Hence dancing not so important and consequently it's attractive to those who dance like tw@ts
Rhythm and Blues (including soul, rock and roll etc) Aimed primarily at hearts and feet. Simplistic but emotive lyrics that press the buttons so people get that 'transported feel' and fairly uptempo rhythms conducive to fancy footwork (think NS, Jive etc)
Funk Altogether a lot more primal. Aimed at the ass, hips and groin and more to do with sex than love or romance. Matybe why people dance prety much the same to heavy funk stuff all over the world.
I know it's a bit of a wobbly theory and it's very easy to think of exceptions, but it's not bad as a shorthand way of explaining the differences and on the whole it's one that works for me