28mm is the optimal size for onroad commuting IMHO.

Light and narrow enough to accelerate and roll well, but with just enough volume to smooth the jitter.

The aforementioned Conti Gatorskins are state of the art. For the puncture prone, Spesh all condition Armadillo or Schwalbe Marathon. The All condition Armadillos have a reputation for a sluggish ride, but in my experience, only the 25mm size deserves this reputation. The 28s run at a lower pressure and have more sidewall (where all the flex is in this tyre) so ride as well as any 28.

Remember that PSI isn't everything as far as rolling resistance goes. A tyre must have enough give to be able to deform over gravel and other bits of road surface or else energy is wasted lifting the entire bike and rider over each micro obstacle. Ever tried riding a solid wheeled skateboard over rough pavement?.

Bigger tyres mean lower pressures, as the contact patch is larger, so less pressure is needed to support the rider. At the extreme end, a 23mm tyre will have a 1 square inch contact patch. Add up the weight of the rider and equipment and divide by 2 to work out the approximate pressure that you need to run in each tyre to allow the tyre to deform to that contact patch.