If we're talking WW vs UF, the scenario can be manipulated to set either character as being the stronger woman, better fighter, or whatever, because we've never been shown what her power level actually is. I suspect both women would be extremely confident, so that's mostly a push.
If we're considering Danning vs. Carter it's a good fight... Lynda has some size advantage, but Sybil seems like she'd have a really nasty streak. That one could also go either way, but if I was betting I'd go with Sybil to eventually find a way to wear Lynda down and negate the size / strength advantage to finally overcome her.
Either way it would be a hell of a battle.
-JM