All you people who are writing about gearing are ignoring a crucial element: gradient.
I used to do some big climbing events in Colorado, where I rode them quite well with 53-39 in front and 12-25 in back. Out there, the grades tend to be lower and the climbs longer, so taller gears work fine.
Now I live in western Pennsylvania, where the climbs are shorter but very very steep - I’ve climbed a hill that has a max grade of 37%. Lower gears are essential.