I play pure F2P survival hunter.
My personal preference for PVP is Hydra ( Tenacity + Mortal wounds ) . Tenacity is good choice for arena or BG - becouse you have panic button Survival of the fittest ( 20% reduces all dmg you and pet for 6 second ) + tenacity bring bonus 5% maximum healt. You can use Survival of the fittest with mark of tyranny + heirloom neck and you have pretty good survival button.
Mortal wounds for pvp is very good choice against any class with healing.
For dungeon soling / farming etc. is best choice Ferocity pet becouse 10% leech .
My choice for soling dungeon is Scalehide pet - very good for tanking ( Ferocity 10% leech , + 50% damge reducing for 12s/60s CD) My personal choice is second pet in PVE Gorilla - becouse ferocity + 60% damage reducing when falling below 40% HP for 15s / 120 CD . Gorilla ability is good choice for combination with Scalehide CD . For example - Your scalehide is in trouble , ability is on CD - you dismiss pet in the middle of fight and cal gorilla for ability. Is optional choice for saving a day but its not necessery.
Short:
For pvp hydra ( Tenacity + mortal wounds )
For pve Scalehide ( Ferocity + 50% dmg reduction ) + Gorilla