Well I'll start off with snake's annoying mortar slide.
This move seems fairly straight forward to punish, just a dropping pound does the trick, and trumps the mortar slam part.
But if snake launches the actual projectile, Jigg's can go straight down with the wonderful air dodge to shield, and roll. Of course snake has ways to punish the roll from here (That infamous f-tilt knee combo, which I won't discuss), so the jiggs should probably roll away from snake. (or do what ever Veril's gonna say)
The other option would be to air dodge diagonally down to shield, and the just grab. Jigg's then has a 80% chance that she will not get hit by the mortar, and has a 40% chance that if she is hit the knock back will not affect her (basing this off of charge levels and mortar height, and the amount of time it takes for jiggs to do her back grab and shield/spot dodge)
All in all in this one example Jigg's has fairly clear advantages.
As far as snake's aerial base goes, his nair is dangerous, but I expect it can be ADI'd out of, or DI'd into for a rest. His Uair and Bair are good as well, but pound trumps them both and so does Dair (to the snake Bair only) The missile is harmless, as are the grenades but his ground set is b****in' against jiggly puff as far as I can see.
Do you think Snake Mainers will respond like the Zelda Mainers did? It's almost feels like having a guest appearance on a talk show.