Most underrated and overrated pets.

[Chaosspawned]

i agree with fox kit for underrated with dazzling dance and howl quite frequently one of my go to pets. And I love the iron star it nukes like a champ.

[Africanleopard]

Waterfly
It's a flying pet with a heal, which is good by itself. It does not simply have a heal, it also has avoidance! This is a very strong combination. This defensive pet has many uses. Avoidance + Heal + Flying racial is great for a stall pet!
This pet is underrated because Teroclaw Hatchling has a similar move set. The main difference is that Teroclaw can choose its type, and that it can heal from the back row. The Teroclaw Hatchling is more versatile, but the Waterfly has higher speed and a strong direct heal.

I am pretty new to the pet battling thing but have been collecting pets over the years.

I was lucky with a rare Waterfly [H/S] and added her to the team to level. And she is a phenomenal critter killer [poison debuff + Puncture Wound] - even at level 21 she could practically solo higher level pets irrespective of type - mind you I hadn't fought any flyer killers on her leveling to 25 . While I was leveling in Deepholm, she was pretty amazing against the elementals as well.

I actually hadn't checked the tier 2 spells - makes her even more awesome.

[Yetimilk]

overrated - fiendish imp, death adder, murkalot, xufu, unborn valk
underrated - p/p frostfur rat, trunks, ghastly kid, dread hatchling, bone serpent

[Maizing]

The Spineclaw Crab is also really good. But its poor rating may be due in part to its rarity, or people using H/H when P/P is the breed that's going to get you real results.

In my experience, it seems to me that, for many pets, H/H is actually a worse breed than B/B. You need specific abilities for H/H to be a good breed... and I don't know of any crab that has abilities that work well with an H/H breed.

Of the new pets, I am really liking the [pet]Axebeak Hatchling[/pet]. Love having a flying pet with a heal. My P/P breed can solo the Pandaren Water Spirit.