I used to pedal a lot slower than I do these days. I'm not sure I got a benefit speed-wise, but I can readily feel what is optimal - if I shift to a higher gear but keep the speed the same, my legs start screaming at me after a while (this is when I am going fast). If I shift to a lower gear my legs spin like mad but don't get tired, instead my lungs start abusing me.
Every person has an optimum cadence where they will feel most comfortable.....
My legs used to be stiff all day at work after commuting but it has been a long time since I had that. I am not sure if that is due to higher cadence (and therefore lower stress on the muscles) or simply the legs are stronger.
As usual, Jur hits the nail on the head.
The general compromise is this. If your lungs are screaming, shift to pedal slower. If your legs are screaming, shift to pedal faster.
If you watched the time trials the other day, you see that most of the pros will ride at about 100-110 when on their own. In a pack, they'll slow the cadence down a little to maybe 90 to save their lungs a little. Having clipless pedals is a big advantage when it comes to turning really big RPM, like 150 or so, but that's only necessary to do that in a sprint. 90 rpm is kind of the accepted sweet spot for most riders. You'll need to 'salt to taste' a little, but with some practice, it will feel normal. It will also be a lot kinder to your knees in the long run not pushing that big gear all the time.