I see no reason to ride on a 25mm tire unless it's the biggest tire your frame will allow. You will notice no speed change at all going down from the 30mm to the 25mm, but you will notice a change in ride quality, as you will have to run the 25s at least 20psi higher to accommodate the thinner tire. The only potential increase in speed (real or perceived) would be brought about by the reduction in rotating mass, not the width. Don't go to a thinner tire, go to a lighter one. 440g is fairly heavy, even for a 30mm. My 700x28 (measure 31.25mm mounted on the rim) Continental Gator Hardshells are by no means a light tire, but still come in at 330g apiece, about 4oz lighter per tire compared to the Specialized. And while I care very little about component weight, if I can save 4oz per tire with no caveats, no sense in not doing it. I would much rather sacrifice 1mph in favor of a bike that doesn't buzz and jitter over the crappy roads I ride on.