The original question was favorite, not fastest. Favorite can be based on feel or even look. It can depend not only on road conditions but the goal of riding. Carrying cargo will change the feel. I notice high pressure is fine on a light bike and even when I have a heavy backpack, but when I attach my luggage to my bike, hitting bumps can be uncomfortable. If I remember right, Heine's argument about efficiency is that the body fatigues from road shock so over a long ride, more suspension is preferable even if it's not more energy efficient as a machine. (I may be extrapolating there.) So wouldn't that mean that it changes depending on how long your ride? My commute is 4 miles each way, and road shock probably doesn't weigh into it much, but on a long weekend ride, it probably does.

And I'd bet the size tires you're used to weigh in as preferable, too.

One thing that someone -- I think Heine -- mention is that narrow tires feel faster because they respond better to "steering input," i.e. the tiny movements we make left and right on our handlebars. Even when you're not turning deliberately, you can tell that it requires less effort on a narrow tire at high pressure. This could create an illusion of faster-ness.

And what about age? The discs in our backs compress over time, so -- spitballing here! -- we older folks want our bikes softer than we wanted them when we were young and foolish. I dunno. Waddya think?

The science is not settled. There are placebo effects, and "feels faster" sometimes translates to "is faster." (And again, is faster the most important parameter?) Also, comparing widths of tires should require us to keep all variables the same. But that's impossible. A wider tire of the same construction is going to be heavier. We could switch to a lighter method of construction to maintain the weight, but now we've changed another variable. The science is not settled, and there are trends in bikes (and everything else) that come in waves.