It's been said that Phil Mickelson and Tiger Woods differ in schedule in one critical way: Tiger plays (and excels) at events with stronger fields while Phil Mickelson excels at weaker-field events.
I've compiled a list of statistics from last season which speak to this statistic. Bear in mind that one season is far from representative (particularly given Tiger's eight wins, two majors, and father's death which forced an extended break). To illuminate true patterns, an entire career (or at least, say, the most recent five years) would have to be examined. The manner in which I've compiled these numbers is assuredly a less than scientific way of determining which player is playing in the toughest events.