They're both very good and viable in most situations.
I think the S/S Ore Eater stands out however due to his speed.
Being faster than a Fiendish Imp let alone alllll the 325 speed pets out there is a huge boon.
You want the option of throwing out poison (which is essentially a DoT AND a HoT thanks to the human racial) or immediately going into Shell Armor first, regardless of what your opponent does.
For 4 straight rounds he's an absolute beast.
Pair him with pets like Scalded Basilisk or Ghadtly Kid who have free swap abilities.
You'll constant be swapping the Ore Eater in and out and his poison allows him to heal on the backline.
This is all good fun...until Graves shows up.
Lately, I've been running S/S Ore Eater, S/S Fiendish Imp & P/P Curious Wolvar Pup.
3 humanoids, I know. Sounds like a bad idea.
I run this team and if I ever meet Graves or Weebomb, I just flee and queue up again.
If you purposely avoid undead AOE teams, it's a very very strong group of pets.