Check out this site for ECS steps and info :
Learn to dance EC Swing with Ballroomdancers.com!
It notes the tempo, basic rhythm as well as the basic steps via video and broken down in a text format - broken down into the lead and follow movements. You might find this handy when comparing the two dances.
I learnt ECS at Fred Astaire dance studio (I guess that's equivalent to Arthur Murrays?) - and then went off to do ballroom competitively, where I learnt ballroom jive. I found there wasn't an awful lot of difference. Generally it's the same - cept you feel like a "grasshopper on heat" when doing the ballroom version cos of it's "bounciness".