I had the pleasure of flying the same aircraft (the same machines, that is, not just same type) in both hemispheres, as part of a long-standing deployment and then back home again.
To rephrase the question slightly, how much difference does the earth's rotation make to a given helicopter if it is flown in the northern or the southern hemisphere?
My carefully considered answer is, 2/5 of 5/8 of f***-all.