I voted Burn for this.
Poison is okay, but I think people are confusing it with the Poison status that the move Toxic inflicts (which is different since the damage per-turn increases).
Burn actually reduces damage your Pokemon will take from Physical attacks. The net gain you get in survivability is far better than letting something tick down to fainted and continuing to take full-damage hits.
Sorry, this was a TCG question *blush*