There are several articles on the subject, but the bottom line (as I understand it) is that for a given pressure, wider tires actually have lower rolling resistance. Note the "for a given pressure" part, because (again, as I understand it) the pressure makes more of a difference than the width. 110 psi on a 23mm tire will feel as hard as 110 psi on a 28 or 32, so there is no real improvement in comfort if the pressure is maintained. However, wider tires allow you to take advantage of the larger air volume and sidewall height by allowing you to ride at lower pressure (say, 70 psi for a 28 or 32), providing a more comfy ride.
If you are on a road bike and can fit 32's, five them a go. In the 700x32 size, the Panaracer Pasela TG offers a very nice ride quality, but many others are out there, of course.

So the question the becomes "how much increased rolling resistance will 32's at 70psi give than 23's at 110 psi?". I don't have this answer, but I have ridden many tires and can say I prefer 60-70 psi to 110+ psi in non-racing use.

Here are some links from a variety of perspectives:
http://velonews.competitor.com/2012/...rethren_209268
http://janheine.wordpress.com/2012/0...ance-of-tires/
http://www.rouesartisanales.com/article-1503651.html
http://www.terrymorse.com/bike/rolres.html

To me, the data is less important than how the tire feels. I prefer a mix of comfort and performance. Alot depends on your use.

If you are commuting, the marginal loss in efficiency shouldn't be an issue vs. more pertinent factors of functionality and comfort (puncture resistance, etc)
If you are racing, consider tubular tires, which have a round profile (providing better cornering feel) and are less susceptible to pinching than clinchers.

Just my $.02, which is most certainly just one perspective.