I would vote Sandboxie if the the poll was, "Which sandbox do you prefer". Sandboxie wins there, hands down. Sandboxie is much more configurable, and definitely has the lead when it comes to usability.
But since the poll is about which has better virtualization, I can't vote because I don't know the answer. I haven't seen anything break out of either Sandboxie or Comodo's manual sandbox. -shrug-