Eh, they're pretty close, but Kong should still have the overall size/mass advantage. Based on various different people's analysis of different shots during the Endgame fight, Scott was roughly 110 feet there. Which is a bit taller than Kong. But Kong has much greater bulk, due to his build.
Anyway, as I have mentioned in previous discussions on this topic, I would personally lean towards Kong, because of the fact that he's much more adapt at fighting at that size and doesn't have a limit on how long he can stay like that before getting tired.
Plus, chances are Kong will totally eclipse Giant-Man once the next film drops.
Yeah as agile as Kong is, he's Tiny. Even Black Goliath made it to 21 feet with an unfinished formula during Project GOLIATH. Scott at his largest means Kong would literally have to climb him like a tree.
Even if we say the tallest Scott made it to was a flat 100ft. Kong still has 75 feet of person to climb before he makes it to his face.