Poision Knife or +3 Axe

[iregev]

Hi,
I have a knife that adds 1 point of poison damage and I have an axe that gives +3 attack and I am wondering which is better to my team.

I am playing a mage with with Undead mostly:
Vampires and Skele archers who deals most of the unit damage
Dark commander (for morale and backup ad their are just cool)
Royal snakes
Inquistors (for rage and the occasional rez)

What do you suggest is better the knife or the axe, I think the knife is great for the archer because of their low base damage but I am not so sure.