As the poster above said: it depends. On a quality tire, with at least 120tpi, it may actually reduce the rolling resistance! On a cheap tire with a low thread count, 60tpi or "unpublished," the tire will feel stiff and though you may not feel it, the rolling resistance could be higher....of course, this discussion of higher or lower is relative to what you currently have, which I am guessing is a mid-range 23.

As for comfort, I didn't;t know what I was missing until I tried it. I can remember the rides and the conversation clear as day that I had with a guy on Veterans Day, 2014....the topic of tire width came up, he told me he was on 25s, recommended it, I tried it the following week....today I roll on 27s (summer) or 30s (winter) on my road bikes, and 32s on my "rain bike", and I can assure you the comfort matters. I live in a land of busted roads, and some are still made with cobblestones. Unless you only ride on pristine, new tarmac....comfort matters and will make you faster.