You should be setting your saddle so that neither your quads or hamstrings engage more.
Sitting further forward and/or higher will engage your quads more while sitting further back and lower will engage your hamstrings more.
You should be working to engage both hamstrings and quads equally.
This gets even more involved once we start talking about cleat position though.
Most people I see have their saddles too high and also have their cleats too far forward.