what they've all said - a lighter, stiffer bike is easier to move uphill, and light enough gearing makes it possible to keep your cadence down and not blow up going uphill, all of which will make it more fun and inspire you to try harder up hills... but fitness still trumps a lot of this. Experience does play a part too, knowing at what level to keep your effort. And some people are just better climbers than others, body weight is often important. I'm a reasonably good climber, but I'm pretty useless on the flats, it's a bit limited how much power I can produce.

But the line between keeping up and not keeping up is pretty fine, so just because they ride away from you on the hills doesn't mean you're a much slower rider unless you're continually barely able to keep up no matter what. On club rides it's pretty common to wait and regroup at the top of hills.