I think Clark Sensei is correct regarding "who" is involved being more important than "what technique or MA" is involved. There are those who would be capable of suriving a real knife attack regardless of how well or badly they are armed and this has to do with some of the things David V. alluded to regarding mindset, will to survive etc. Then there are those who are so good at taking life with a knife you would come out on the bad end even if you had a machine gun. In relation to something Sensei Ledyard said on another thread - a good knife attacker does not fight, they ambush.
"Who" we are dealing with is quite important imho. My vote was based on knowing at least 2 people who trained with me in Aikido for less than a year who were able to get away without injury when attacked with a knife. The reality is that any Aikido skill they had may have a lot less to do with the result than either person's will to survive or the knife attacker's resolve to take them out. No two situations are the same in this regard and it is diffiicult to state categorically what the outcomes can be.