The only place I've ever used a magnetic angle finder is when bending pipe too big to easily remove a little bit of over bend or when trying to match existing bends from the previous electrician.
You never know if his bender was off by a degree or two and mine seem to almost always be a little off.
I think that after a bit of use, the jaw, if you want to call it that, will spread a little which leads to a slightly lesser angle of bend than the marks are telling you.
That angle finder does come in handy when bending 4" though.
couple that with a "no-dog" and you're good to go.
As for personal taste, I like Benfield for hand bending
