http://anydice.com/ is a cool site to type in dice and get averages, etc.
Here is a link for those particular weapons.
Serpent's Bite slays humanoids, poisons, and gives extra crits. It'd probably be good to make sure you have some weapon marks in that skill for the orb guardians, etc, but the mace will have the highest rolls (not factoring in the crits or poison)
Edit: The effect of slaying is that any successful hit will be a critical hit. The message generated says you hit "with full force", and these attacks will deal double damage.
Just a note, but missile critical work slightly differently. Plenty of info on the Wiki (if you don't mind being spoiled a bit). Otherwise people are generally happy to help.
Last edited by Kyreles; 01-16-2016 at 03:13 PM.
Proud member of Team Silfir in the Treasure Hunter debate.