I can't speak to how different Claire A / Leon B is so it may be a more radical departure.
Somehow I doubt it, I think the scenario A/B and dual story thing was more of a
for fans who wanted as much connection to the original as possible rather than something that they couldn't have worked around in a single playthrough.
Scenario B Claire does have original stuff in it. She gets to enter some rooms Leon can't, she deals with Sherry and someone else instead of Ada, she gets her own weapons, and it gets you the true ending. It also unlocks the 4th Survivor challenge mode. It certainly isn't all original and it's 80% what you did in Leon's, but basically Leon A/Claire B is the full campaign, even if Claire B isn't all original stuff.
That's cool, thanks for the info, even 20% bumps it further up my replay list than there being nothing there.