The Pantera has the highest base Strength among the Basic pets. Along with decent Physical Defense and Hit Points to take a couple of hits (especially higher staged Panteras), makes the Pantera the most versatile and arguably the most useful of the Basic pets.
The Poultry's stats and skills focuses it towards Dexterity and Physical Accuracy. This makes it a useful companion to melee classes who like to fight monsters high above their own level. However, due to its mediocre defenses the owner must ensure the Poultry never attracts the attention of whatever it is fighting.
With the highest base Vitality of the Basic pets, the Tortus is the ideal tier 1 pet if you are looking for a tank pet or as a support pet for a tanking class. Its Unity and Enchanted skills significantly reduce the damage it receives, while the threat modifiers in the Tortus' attack skills help it to hold aggro.