I’ve used one for years and I think they’re a little bit better, in that for me, it means I’m less likely to spin out on techy climbs and I’m less likely to stall in them ‘oh shoot I’m in the wrong gear’ moments. As for being able to pull a bigger chainring / higher gear / be faster up climbs / more attractive to the opposite sex claims made by the marketing peoples, they’re mostly bullshit.
So in summary, they’re a little bit better for the same price.