Big Mom with her abilities would pose a much bigger threat than Whitebeard was at the time. He may have been the World's strongest man at some point in time but he was only a shell of himself at Marineford. We all saw the destruction he caused with a basic devil fruit. Whitebeard and his powers are pretty straight forward, he is a fighter with a fruit that amplifies his power and style.
Big Mom would cause a lot more problems with her abilities. Just the sheer amount of people that would be unable to harm homies would cause a lot of problems for the marines. Add her super tough skin and monster strength to the equation and you basically have a more dangerous version of Whitebeard, with a bit less raw power.
Her family was also affected by the power creep because if Marco's and Dogtooth's introductions were swapped, we would have a much better image of Marco than we have now. Big Mom's family has a lot of fighters again with a myriad of tricks that would cause a lot more trouble than people like whitebeards sub-commanders who have basic abilities.
That said, everyone at Marineford didn't get a fair shot and we need another Marineford to create a new benchmark. Marineford played out in a pre-haki time for the reader. So besides some hints here and there and some people shouting omg haki ! nobody showed any significant haki feats. If that war would play out now is there any question that most top dogs could go full body haki if they wanted to ?
So Big Mom and Crew to save Pudding from pre haki Marineford Marines would be a Big Mom victory. Because the sweet commanders, Oven, Daifuku, Perospero, Brullee and the enraged army seems a lot more dangerous than Blamenco, curiel, Namur, Fossa and Izu. The only scary ones are Marco, Jozu and Vista and I believe the sweet commanders can keep them at bay.
Momma can go wild with Zeus and Prometheus. Ride a tidal wave homie around the plaza. Make a magma and ice one of she feels like it.
