Which auto-axe mod should I get?

[Osmium]

I just realized that I got up to 85 stamps tonight and I can buy a mod for my already ridiculously overpowered auto-axe. The options are fire, electricity, poison, or double speed at the cost of 33% less damage. What's the difference between the mods? If I were to try to apply logic from other games, electricity usually stuns, poison does more damage but wouldn't work on robots, and fire is a more general option. The wiki says they all do the same damage except poison does more over time.

[slippingsnake]

not poison.
it works good on some enemies but not robots.
Also the green cloud around a poison-Axe looks cool but covers more of your screen :)

I stick with fire but also tend to switch to chainsaw.

[lucg]

I run it with "electricity" mod ... . Didn't remember before applying it, but I shred a trog in 1 second ... !

[BizarreMan]

Fire so you can slot Friendly Fire and heal mobs up.