It depends. As with most bicycle things these days, the gains/losses are miniscule and not measurable by 99% of cyclists. Another variable can more than eliminate the rolling resistance benefits of wider tires. Depending on who is selling what, the rolling resistance gains of a wider tire either overwhelm the additional aero drag or are overwhelmed by it. It depends on pressures. It depends on road surface. It probably depends on wind direction and how heavily the tires are loaded.


I'm not denying the potential benefits of a wider tire -- for three years, I held a road Strava segment KOM where I was riding 38mm tires at 55 psi! I'm just saying that there is little, if any, way to know for sure what the NET impact will be. The gains/losses are so very small that it almost doesn't pay to think about.


But if your primary objective is added comfort . . . go with the wider tire at a lower pressure. Comfort is something you can sense. (And who cares if it makes you 0.3 mph slower?)