There's also species resistances/weaknesses and species abilities as well. =)
Between the three pets, the Poogle and Draik both get a 10% resist to fire and earth (none for Kougra) and both can get a six icon species ability attack when leveled up high enough. Pretty much a toss up between the two unless you want to take the icon types of the species ability into consideration (Draik -- Fire, Dark / Poogle -- Air, Light) and the level needed to get the full use of the attacks.
Draik :
http://idb.finalhit.org/?searchtype=specie&specie=draik
Poogle:
http://idb.finalhit.org/?searchtype=spe ... cie=poogle
There are probably some better species out there, but it would really depend what you need at the moment. In other words, someone who meets a bunch of Ghostkerswords may want to consider a Pteri (40% air resist) while someone who fights against fire icons would consider a Scorchio (30% fire resist).
Take species weapons into consideration. That's why many people use Kacheeks or Elephantes (good healing, cheap attack items).