Hanabusa is the worst.
Not sure why people think she'll defeat him so easily. It'll be competitive, for sure, but she lost to Schatz in 2010 after he was appointed by an unpopular Governor despite having the endorsement of the legendary Sen Inoyue, so she's certainly not infallible. While I don't know too much about Hawaii politics, one would think voters in Hawaii would start to see through Hanabusa's opportunistic tendencies. And Vega raises a good point about seniority.
Obama endorsed Schatz in 2010 over Hanabusa. A severe tropical storm lowered turnout in a lot of the Asian-American heavy precincts in Hawaii. Even if Schatz was appointed, he was still an incumbent, and if I recall correctly, no incumbent Senators has ever been defeated in a re-election campaign before in Hawaii.