Ahem - nice try.
Since you seem to have the stats handy, please provide number of matches across which you compute the %. Obviously, the deeper you go into tournaments, the less success you can expect in breaking serve. Also include the metric "avg matches won per tournament". A better metric would be return points won, instead of return games won (Fed sucks at bp conversion - not really reflective of his return ability).
in all examples the first number represents 91-99 period for sampras and 01-09 period for federer, and the second number 93-99 for sampras and 03-09 for federer
1) the number of matches
sampras 347, 289
federer 413, 353
increase of 19%, 22.1%
2) the number of tournaments played
sampras 83, 68
federer 108, 86
increase of 30.1%, 26.5%
hard courts replaced carpet, which was main surface back then in the post US Open period, plus it was common in the period after AO and before Indian Wells. increases we see here reflect that.
increase of tournaments played in both examples is also bigger than increase in played matches.
3) average matches won per tournament
sampras
295 matches in 83 events = 3.55
248 matches in 68 events = 3.65
federer
353 matches in 108 events = 3.27
304 matches in 86 events = 3.53
sampras ahead in both comparations. i double checked it, it's true.
4) bp conversion
sampras
43%, 43.6%
federer
41.4%, 41.6%
well, if federer sucks on bps, sampras wasn't much better in a given periods.
return points won is a mess on ATP site for all 90s players, so we cannot compare.
so, let's see what we have
-your evaluation of their skills which are the most important to accomplish the break
-sampras played on a surface which was faster compared to federer's time
-sampras wins more matches per tournament in both comparations
-sampras trails very little in return games won in both comparations, much, much less than expected
-he even wins year by year comparation in both comparations
-higher best performance
-those statistics are all from huge periods of time, not a few tournaments, or a few months. both examples contain their best and most productive periods.
again, i ask how is all that possible?