Really depends on how much you ride. When you upgrade yorlur bike you aren't really just getting a lighter bike. Weight reduction comes with higher quality components and frame.
An upgrade in components and frame will mean the bike rides smoother, usually. It is also more responsive in handling, acceleration, and shifting. The components become more reliable and you'll gain a bit in shifting capability as the number of gears increases.
Lighterweight wheels means you'll be able to climb faster, too. The bearings will roll smoother and wheel build stiffer, for improved acceleration.
Comfort also plays a part in an upgraded bike, but only if it fits you properly.