I personally feel as if the list is based on hype/appearance rather than their usefulness. Most pets are useful in battles. I would recommend leveling pets that you feel strongly attached to.
If your goal is to beat the Celestial Tournament i would recommend this guide: http://us.battle.net/wow/en/forum/topic ... 513?page=1 https://docs.google.com/document/d/1WRF ... edit?pli=1
Pets that I love for the Celestial Tournament:
Nether Faerie Dragon
Rabbit / Hare (pref the version with the highest speed, you can capture a lvl 25 one)
Parrot P/S or S/S
Any fast Flying pet with Stampede/Flock.