Yet another reason to only amplify mu conclusion. This hype over the slow courts is way overrated!
Wellll, one of the big differences now is the balls. The allowed size range is not large, but ten years ago most were on the small side, now they're all on the large side. They also tend to fluff more nowadays, partly because the increased friction of the court surfaces tears them up more easily.
Tennis adapts to the conditions it is given though, so inevitable we see...
1) Higher bounces mean a higher playable strike zone. As a result, more tall players on tour.
2) Slower surfaces/balls means either longer rallies, which favours consistency and stamina, OR enormous baseline power to hit through it (thus more really big guys).