Nope, based on plenty of their matches that I have seen, unlike you hardly knows anything about Sampras.
Federer vs roddick in uso 06 final :
115.57 mph 1st serve speed average
93.83 mph 2nd serve speed average
Federer vs roddick in wim 03 semi :
115.57 mph 1st serve speed average
97.56 mph 2nd serve speed average
Federer vs roddick in wim 04 final :
117.44 mph 1st serve speed average
97.56 mph 2nd serve speed average
Federer vs Sampras in wim 01 4r :
114 mph 1st serve speed average
97 mph 2nd serve average
Yeah, big a** difference in serve speed of young fed and older fed.
Meanwhile Sampras in that wim match :
121 mph average on 1st serve
110 mph on 2nd serve
Radar guns used to measure the speed at the net earlier (in the 90s if I am not wrong), but they measure it from the server's point of contact(i.e when it hits the serve) from some time in the 00s (if I am not wrong)
Anyone who actually saw them both play and has half decent eyes and head can tell that Sampras's serve was clearly faster. (By a significant amount)