Tough call. On the one hand, walking the plank gives you a chance, although very small, at survival. But with a hungry crocodile in the water and probably no land for miles in any direction, you will almost certainly die, and that death would be a lot more painful and prolonged than a swift, clean blow to the neck.

I'll give it a 50/50 of this, I find Beheading is Cruel, Gruesome, Gory and not very Clean, But I prefer Walk The Plank, Because I could swim back to the island very safely, Walking The Plank is better than Beheading.