sampras was too strong mentally for agassi
he made tennis his priority, agassi didn't
agassi was able to beat him when it was a slow hard court (miami, australia, canada etc) or clay (obviously)
but, wimbledon and us open are the 2 most prestigious slams, historically
you can say that the us open has been a joke in terms of organization the past few years, but it's still behind wimbledon in terms of prestige and worldwide interest
sampras won their matches there, and more to the point, he won the big matches when it mattered. 4-1 in slam finals was it?