What's the difference in gamma knife radiation and external beam radiation?

I am 30 years old I was diagnosed with a AVM in my visual cortex area. My Nero gave me the option surgery or radiation I choose radiation because surgery could cause blindness well mine is small the size of as pinky nail and has not bleed yet they said that the beam radiation would be the best I’m just afraid I the time frame it will bleed? I don’t know if I am doing the right decision or not ? And in the time frame what if it bleeds what my next option more radiation or do they do sugary?? Please help need advice