There are two lines of thought for this. There are many that will say the abatoir for all the right reasons and I agree with everything said and why.
On the other hand, we use a home kill butcher for our own consumption and it has always been, humane, proffessional, done with kindness and respect for the animal, no stress at all for the pig or us, and the pig has been lead by the bucket and the shot taken when the head is in the bucket and the pig knew nothing. We hang in the cellar and he returns to butcher. He is the kindess man you will ever meet and is very reverend with the animals and a pleasure to know.
If you are lucky to have a butcher like that go for it, if in doubt, take the other route. Ours was recommended by another party who has used him for years and that is the key I think, choose one recommended for his skill and dedication to the task and puts the welfare of the animal first.
There is a phrase often used on this subject, 'I don't understand why anyone would ........'
There is a very good answer to that, it comes down to personal choice.
Kate