Due to the ability for clubbing blows to stun the seal. Not only do seals feel less pain during the clubbing, but also move around less and so suffer a quicker death. Rifle shooting on the other hand, forms a smaller wound that does not usually stun the seal. The seal may move around and suffer a slower death, or it may escape, causing it to become food for many predators. Furthermore, it is much harder to land a clean shot from a moving ship or ice block than it is to bludgeon things to death.
However, due to recent legislation against seal clubbing, rifle shooting seals are now the only legal, efficient, and sufficiently compassionate way to hunt seals.
Well many of those who support that legislation likely have the end goal of ending all hunting for fur, so they'd likely use such information to simply justify further that the hunts should be outlawed all together.
That pink rifle though, reminds me of those pink "my first rifle" guns that are sold. Kind of just had me shaking my head that they exist, but I guess I feel that a gun should... well look like a tool/weapon and not a toy.
