The half-life of Cialis is a LOT longer than Viagra's, as well, so it's like comparing apples and oranges. Both are fruit, but one has a higher glycemic index.
they both worked entirely different for me. the viagra gave me a raging and painful hardon that lasted for a long ass time, the cialis just got me to a "ready" position so to speak, a semi if you will, from there it was extremely easy to reach a VERY hard erection many times over.