Friendlies anyone can play amazing. Nothing is at stake but pride maybe. This only goes for certain people.
Tourney matches on the other hand are based on who can clutch out all the tech skill without choking. Along with this it takes a proper, calm mindset to win. Making the right decision when all the pressure is and succeeding really proves who the best player is. You can't get frustrated because your losing. In fact, I get excited when I play players I don't know when i'm behind. I play much better.
I would say a good example of this is shiz vs Lambchops. Sure they are just vids but Shiz doesn't **** up. Dudes spot on everything. Lambchops will **** souls but he will/or did **** up, get pissed, and make HORRIBLE decisions. saw it several times when i watched the dude play at FC-D.