Originally Posted by
sam_cyclist
Perhaps, but you'll also go faster on a heavier bike on the way down.
But seriously, in reading some of the threads on this forum, many forum members report that their ride times don't improve with lighter or more expensive bikes. Some even report that they are a bit slower on their lighter bikes, for whatever reason.
I don't know who reported what but there is no question that shaving 3-4 lbs will make you faster up a 5+% hill. An aero bike with a good set of wheels could save 20+W on the flats which is substantial. Whether any of that matters to you is a different question.