It's tough to say. Massa improved a hell of a lot as a driver last season, and after coming so close to winning the title, he'll no doubt believe he has unfinished business and want to go one better. On the other hand, Raikkonen is the more gifted of the two, and if he puts in the required amount of effort, you'd probably expect him to shade Massa over a season.

Ayrton Senna: WDC 1988,
1989, 1990, 1991
McLaren: WCC 1974, 1984, 1985, 1988, 1989, 1990, 1991, 1998,
1999, 2007 McLaren: WDC 1974, 1976, 1984, 1985, 1986, 1988, 1989, 1990, 1991, 1998, 1999, 2008