Realisticaly, neither one's legs would be able to support their weights.
Petey simply can't survive in the real world. He lacks roots so he can't absorb nutrients from the ground, since he is that big he would require enourmous amounts of insects or living beings to eat to sustain himself AND without water, his cell walls would get weak and he would get crushed under his own weight. And Petey has balancing problems because of his enormous head, basicaly giving him the same problem as Duon.
But then there is the fact that....porky is technicaly on suspended animation and he is technicaly dead by real world's standards. And without his legs, death rays OR movility, Porky can't do anything.
So it's up to you people.....if you decide that porky is dead then Petey wins, if you decide to treat his suspended animation as that, then it would be the most boring and long fight to date with Porky winning by default.
It is basically:
dying man-eating plant vs evil and very frozen old man
1000-0 on Porky's or Petey's favor depends on your decision.
p.s, these boss fights are a joke.