>>715028825 (OP)Sonic and Shadow's fight in the jungle was a tie as it was interrupted. I'd say both were evenly matched there.
On the Ark, Sonic absolutely annihilates Shadow. He humors him for a bit and then dusts him, reaching the cannon and destroying it. Shadow kind of lets that happen though since he doesn't give a fuck about Eggman. He knows the doomsday program will activate all according to plan once the emeralds are put in.
And no the cannon being destroyed doesn't impact future stories as SA2 is the last Sonic game.