Which martial art for self defence?

Krav Maga would be your best bet in this instance. It is one of the most effective self defense methods up there with arts like, jeet kun do, hapkido, taijutsu, and a few others. there is no best martial art by any means but krav maga is a very good one for self defense, the only thing to be cautious of is their gun defenses... which in many cases I have seen are incredibly flawed, their hand to hand, ground, and knife defense is very good though... good luck in your training