i live in england and prefer lighter bikes because i live at the bottom of a valley with 800 feet clims in each direction. I really notice the difference in bike weight. however people do get obsessed about the weight of their bike and how a bike goes. A biek will only go as fast as the guy person pedalling it and how long they can sustain that cadence for. I think aerodynaics is more important than weight, i had a aero fork and then a normal fork and i lost 2-3mph on the top speed of the bike.