Laser bean or grapes of wrath?

So grapes of wrath will do a guaranteed 6 damages but if you can sneak a laser bean into the board, it kills one zombie, deal 4 damage to the hero, and will deal another 4 damage to the zombie hero next turn assuming that it does not get rocketed or lucusted. Which one is better? Sun cost doesn't really matter as 6 sun is just a tiny bit less than 7 sun.