Full. It's gotta be. It's not like they kill you in different ways - both work by cutting off the arteries in the throat and creating a 'blood choke'. Both carry the same risk of brain damage if the process is interrupted - and interruption is a lot more likely in Partial where you can easily interrupt the process yourself. The only time Partial is the way to go is if you truly have no access to a high enough anchor point - and in that case you might want to just use a different method altogether.
If you're interested in hanging, I always recommend reading the Japanese Suicide Handbook - it has a lot of reassuring things to say about Full Suspension hanging.