Torpedos pistol I/M

[RussaX37]

I know there is many repeating questions but I didn't find correct answers.
So if we are talking about impact torpedos which need to hit target to detonate the other one magnetic dont need to hit target so it can go even below the boat to detonate.
My question is what is the maindifference and when is which good to use so let's talk about positive and negative sides because with magnetic torpedos I got many problems with hitting target on angle so it just repel and dont explode but infact angle is like 40 degree which is not that bad.