Why is it assumed that if you spin you are unfit? If you watch pro cycling you will find that the best climbers will generally be in a lower gear and turning a higher cadence, whereas the sprinters will be running bigger gears and grinding to the top – Just look at the cadence that Lance Armstrong use to climb at.
I used to ride in a big gear and grind my way up, but in the last couple of years I’ve tried to train myself to be more of a spinner: At first it was hard work but I’ve got used to it and now I find it is much better, particularly on long climbs that have a gradient that varies. Spinning may, on the surface seem the easy option, but keeping a high cadence is certainly hard work and takes some training.
Ultimately, someone who runs a compact will be able to ride just as fast on the hills as someone running a double, albeit at a higher cadence, which is supposed to be better for endurance.
Big gears are often run by people who think they are better than they really are.