From a purely statistical POV: much higher unreturnables, an advantage compounded by playing in an era with lower avg unreturnables (part of this is due to the “giant” skew, but this holds even when adjusting for height; a quick perusal of TA charting stats evinces that).
If stuff like Sampras maintaining or even ramping up his unreturnables against better competition (i.e “being clutch” — really, the lack of drop-off when facing Top 10 opponents is nearly unprecedented) sounds too airy fairy, the first paragraph should at least be enough to not dismiss the comparison out of hand.
As for the myriad of variables you’ve gone over: I believe their collective impact is overblown relative to the effects of poly. See below, snipped from our last exchange:
You would expect there to be at least some kind of statistical footprint left by all of these factors, perhaps even just gradually. Instead the year-by-year service statistics of the last 10-15 years are virtually identical. With all of these moving parts, you would think one or the other will lead to real changes in this-or-that service statistic, if not at once then at least over time. It isn’t happening. Unless they’re all cancelling each other out in near-perfect harmony, I have a difficult time believing that all of these changes amount to such a negligible impact on the bottom-line.
Tour-wide first serve % jumped about 3-4% in a four year span coinciding with the mass-adoption of poly. It’s increased by about a percentage point since then, 15-20 years later. What would that indicate?
I do admire the rigour with which you analyze things (and agree with the analysis most of the time) but you could perhaps go without assuming that others are missing something when many of your contentions are disputable and, from the statistical side of things, occasionally quite hard to justify. It’s very possible that many folks on here have actually spent quite a lot of time poring over the things you discuss in this thread and yet still, on eminently reasonable and dispassionate grounds, disagree.
Also, fwiw, I don’t consider Sampras to be a better server than Karlo, Isner or Opelka. Hurkacz, different story.