Maybe it was rude calling information from your friend "hearsay", and it was not my intention to turn this into some sort of big argument. However you stated, that SnG activity on PartyPoker is "larger than anywhere else you checked", but as my small check show, SnGs on PartyPoker basically dont even run at certain times of day, whereas on PokerStars there is 24 hour activity. Logged onto the PartyPoker lobby again this morning, and during the 5 minutes or so I watched, not a single player registered for a 5$ SnG.
So presumably your friend play only during peak hours, and to play 20 games per hour he presumably also have to play several different formats and limits. If he play 200 games per day, that is something like 10.000 hands. That mean, he is mass multitabling, and if you are willing and able to put in this sort of volume, and you are a winning player, you can grind out a profit in many different game formats on many different sites.
But most CC members are recreational or part time players, who dont put in even a fraction of this volume. Personally I can play up to 2.000-2.500 hands in a day, but only when I am not working, and then I am pretty exhausted afterwards. So for most people a leaderboard does not matter, because we will never get anywhere near it. That being said the rake is lower on PartyPoker for some SnG formats. So that can be a legit reason to play there. But PokerStars offer more different formats, and as already established there is much more activity on the site.