Sigma vs. pi

[005199302]

If length and strength are inversely proportional to one another, why is it that sigma bonds are both larger and stronger than pi bonds?

[skyeblee2F]

Their difference in strength has to do with their overlap. Sigma bonds are characterized by end-to-end overlap while pi bonds (which occur between "leftover" p-orbitals) overlap in a side-to-side fashion.
As you can see in the image below, the head-on contact allows much more overlap and thus more strength.