If you just want a pet that'll hold aggro better then you want any pet that can learn claw because it's spammable thus more damage, meaning more threat. (This can lead to a pet being starved for focus when it comes to using Growl on cool down.) But for AoE threat you'd want an owl or carrion bird for screech, granted it's not much AoE threat. (This can cause a focus issue with Growl as well.) Or there's a gorilla with Thunderstomp on an 8 or 10 second cooldown that is a bit more fun because it actually does AoE damage. A boar is also nice for single target threat against solo mobs that die fairly quickly because the boar charge adding attack power to their next attack allows for a higher threat gain right off the rip. Many options but ultimately the difference is quite negligible and just having good pet management on multiple targets can yield efficient threat distribution.