As for the fight, it's up to what you choose to consider. As far as battleboards are concerned, Alpha-152 had few concrete feats before dying, since most of her fights were in-game rather than cutscenes. Even Kasumi Alpha got more love(got to kick Ayane around). We're forced to powerscale here basically. What we assume is Alpha-152 fought off Hayabusa, then an Ayane/Hayate double team, then Kasumi before finally going down. She is also capable of shapeshifting and using ninpo.
I'd give Alpha-152 the nod, as I believe Heihachi is simply below that level. Like I said though, it's based mostly on powerscaling and implications. Not much else to go on.