You can try and find out yourself !. jokes apart threading is much efficient, twiser can pluck only one hair at a time however in threading more than 3-4 can be removed at one go and result is much cleaner as it removes very fine hair too. So for thicker eyebrows its much efficient than twisers and hence preferred. I could say if anyone has tried plucking and threading both, will prefer threading, of course exception could be there.
The difference between threading and tweezing is that threading is done line by line- while you can pick out an individual hair, you can pick off a whole bunch of them as well. Its much faster, and a lot less painful.
Also, for some reason (someone else maybe able to give more info here) I don't seem to get as many problems with ingrowns etc with threading.
And you get a much better shape out of them- though that's probably my ineptitude at tweezing, more than anything else.
Going by the info on the thread, am glad to hear that eyebrow threading is done here in Zurich/Zug. I would also like the contact details of the lady. Can someone please PM me as well?
Sajeeka beauty parlour on Heinrichstrasse is another good one. It is a Sri Lankan parlour but they are pretty good at threading. Roshi that has been recommended above is also pretty decent.