For a game theory analysis of Nadal-Federer encounters check this. Admittedly interesting but just trying to skirt around the fact that Rafa simply rocks.
What you didn't click the link? Perhaps the conclusion of the piece will get you interested.
When choosing the right mix, it is not just about playing to your strength. It is important to play to your advantage, which may require you play your weakness more often. This becomes even more important as your strength improves!