DocDore wrote: a defender in the inbounder's face makes it much more likely he screws up--especially in a high-pressure end-of-game situation.
Rick Pitino still wishes he had put someone on Grant Hill when he threw 3/4s of the court to Laettner in 1992. Having someone in your face rarely disrupts an inbounds pass. I think you'll find most coaches will do both, depending on the situation.