Webb PB's: 1:45.80, 3:30.54, 3:46.91, 7:39.28, 13:10.86
Willis PB's: 1:45.54, 3:32.17, 3:52.75, 7:44.90, 13:27.54
Obviously, Webb has the better collection of PB's. This is usually how one runner is compared to another. The only argument for Willis' superiority would be if he had experienced significantly more championship-level success than Webb, which he hasn't, or if he had established a history of consistently beating Webb in head-to-head situations, which he hasn't.
Imagine that Webb and Willis stepped onto a track for a 1500 meter match race, just the two of them. If you had to bet your life on the outcome, would you honestly pick Willis? Given what's happened in the last 6 weeks?
Webb is at a level right now that Willis may never get to.