Its possible to leave sapwood on and not have checking too. You need to leave the bark on and dry slowly, and it takes a little luck. I happen to have a couple of staves with intact sapwood, I've been toying with the idea of leaving some sapwood on at least one of them. They are thick enough that I wouldn't have to, so it'd be a gamble. I do think the sapwood is probably a little lower in mass, since the heartwood does contain a good deal of extractives. And it should still retain much of its elasticity since most of this would come from the fibers.
I tend to agree with Ryan though, I have to think that if there were a real advantage then you'd already be seeing it done.