Most families are unique in certain ways.
For PvP, let’s say I want a pet that reduces healing.
My options are Rodents, Lizards, Carrion Birds, or Hydras, if I want a pet with a Mortal Strike, 50% reduced healing ability.
Now, within these options, there are more sub-options.
Rodents are Cunning, so they give an extra speed bonus and their special pet class ability that all Cunning pets have, is a root-break.
Carrion Birds are Ferocity, so they give a little bonus to leech (lifesteal) and their Ferocity pet ability is basically Bloodlust/Heroism, the Hunter version.
And finally, Lizards and Hydras are both Tenacity pets. They give a 5% bonus to total health, passively, and an additional defensive cooldown as their Tenacity ability.
Since we don’t get the freely pick the specs our pets have, it’s pretty limiting what pets you can use, especially if you want a certain aesthetic.
I try to stick to using sea creatures since I’m a KT, for example.
It’s mostly just another form of cosmetics, but pets actually do have combat purpose so it’s a little more than that.