Hello, I think the second one Phobos pet will be best for doing war. I see this pet has such a great vondo points and 15% extra chance for not getting hit.This will help you to keep your army alive for long time and this will help you to destroy quickly to your enemy.
And the first one, Undine

is not also bad for war because it has also hit chance by 5% and reduce hit chance 10% this will be helpfull too in a war battle.
But from my mind i will like to suggest you the Second one Phobos pet. You may still get help from best gamer.