There are a total of eleven different Ferocity pet types to choose from in the game, three of which are Exotic and only available to Hunters with the Beast Mastery talent. Each pet has a unique ability, some more appropriate for a raid environment than others.
Demoralizing Screech: Blasts a single enemy for 85 to 129 damage and lowers the melee attack power of all enemies in melee range by 410. Effect lasts 10 seconds. 10 second cooldown.
Rake: Rake the target for 47 to 67 bleed damage and an additional 19 to 25 damage over 9 seconds. 10 second cooldown.
Tendon Rip: Tears at an enemy's legs for 49 to 69 damage and reduces the movement speed by 50% for 6 seconds. 20 second cooldown.
Serenity Dust: The moth's wings produce a cloud of dust that increases its attack power by 10% and heals it for 825 over 15 seconds. 1 minute cooldown.
Savage Rend: Slashes the enemy with the Raptor's talons for 59 to 83 damage, and causes the target to bleed for 21 to 27 damage every 5 seconds for 15 seconds. Successful critical strikes with this ability temporarily boost the Raptor's damage by 10% for 30 seconds. 1 minute cooldown.
Dust Cloud: Your Tallstrider kicks up an obscuring cloud of dust, causing all enemies within 10 yards to miss their next attack. Lasts for 8 seconds. 40 second cooldown.
Sting: Your Wasp stings for 64 to 86 Nature damage, and decreases the armor of the target by 5% for 20 seconds. While affected, the target cannot stealth or turn invisible. 6 second cooldown.
Furious Howl: Increases melee and ranged attack power by 320 for the Wolf and its master for 20 seconds. 40 second cooldown.
Lava Breath: Your pet breathes a double gout of molten lava at the target for 128 to 172 Fire damage and reduces the target's casting speed by 25% for 10 seconds. 10 second cooldown.
Monstrous Bite: Your Devilsaur ferociously bites the enemy, causing 91 to 123 damage, and boosts its own damage by 3% for 12 seconds. This effect stacks 3 times. 10 second cooldown.
Spirit Strike: Burns the enemy for 49 to 65 Arcane damage and then an additional 49 to 65 after 6 seconds. 10 second cooldown.
Right away, we can eliminate abilities that are obviously not entirely geared towards pure PvE damage output such as Tendon Rip, Dust Cloud and Lava Breath. Abilities like Sting and Demoralizing Screech are also of questionable usefulness, particularly when you take into consideration that neither will stack with other armor and attack power reducing buffs you'll likely have in a raid environment. This puts Carrion Birds, Hyenas, Tallstriders, Wasps and Core Hounds out of the running for viable raiding pets.
In order to determine a relatively accurate case study comparison of the remaining pets under ideal circumstances using a controlled data set, I used Shandara's Spreadsheet to compare pet dps for the remaining pet types. For the sake of simplicity, I used the character profile that loads by default (Shandara) when you first download the spreadsheet so that it would be easy for you to follow along with these figures yourself to check the math if you so choose. By simply swapping out which pet is active on the "Pet" tab of the spreadsheet, you'll see how each type of pet's dps differs when all other factors remain constant.
For Hunters not specced into Beast Mastery, you'll find that Cats still provide the most overall dps (1115.46 in our spreadsheet example), followed by Raptors (1099.30), Wolves (1087.99) and Moths (1080.06). This means a 16.16 dps gap between the highest dps pet and second highest dps pet, and a 35.4 dps gap between the best and worst. Some could argue that a difference of 16 or 35 dps is negligible at best, and in that case it merely becomes a matter of personal preference. For the Beast Masters out there, you'll find Devilsaurs are the best Exotic pets in terms of dps, with Spirit Beasts coming in at a relatively distant second. So, while Rake may deal less damage per swing, it's significantly shorter cooldown gives it the edge over a Raptor's Savage Rend. For Exotic pets, the stacking percentage increase to a Devilsaur's damage gives it a distinctive advantage that will scale nicely with your gear.