Uh oh, I hope I can live up to your expectations!

Jive music is faster. I don't have the recommended tempos at hand, but it's fast.
There is some choreography that's unique to each style syllabus-wise, but they're all certainly interchangeable.
Style-wise, jive tends to have higher knees and feet coming up higher off the floor, while ECS tends to be a bit lower (although some people dance it with the higher knees). In addition, the footwork is slightly different: in ECS, the triple steps are side-together-side, while jive is in place-in place-side.
In short, they're similar but different!
