I don't think the size matters... sensation is provided by the nerve bundle that's been wrapped inside the skin, and that is the same number/sensitivity of nerves (which varies by patient) regardless of how big the "wrapper" is. A larger clit may be easier to access, allowing for better stimulation, but that's not the same thing.
Of course, that's also why the reduction is, unfortunately, a risk; any time a surgeon messes with those nerves, there's a chance they won't recover.