It's been awhile since I revisited the DBZ movies, so some of this may be a little off.
Scenario 1—
Broly has the raw power advantage. Against Goku, he was almost toying with him. Clearly exerting the maximum power he had, but nonetheless wasn't trying to instantly crush Goku. Contrast to that, Cell found himself worked up enough by his fight with Goku, that Goku believed Cell needed a Senzu bean to replenish his lost ki. While Cell wasn't all out against Goku, it seems like he was giving enough effort into it.
The only questionable aspect is if Cell's regeneration could play a role in getting a sneak attack off at Broly's abdomen scar, his very obvious weak spot. I'll say, probably not.
Scenario 2—
Super Perfect Cell should take this easily. SSJ2 Gohan's ki was cut dramatically, sure, but it was still far more than any other Super Saiyan around. All of whom are more or less comparable to Goku, just weaker. He should be strong enough and fast enough to penetrate Broly's abdomen and end him.