I had it done a week ago as my front passenger side has started to be eaten up by rust. Bought one from ebay for £35 delivered what a steal..
It was a pain in the **** to be fitted tho. initialy I thought its going to be a piece of cake, held on by a couple of screws.. oh boy was I wrong...
Ended up with a 5 hours of cursing,blood and sweat.. but after all done.
A bit of advivce get some replacement screws for the wing,front bumper and side skirts, as when you start removing them (You'll have to in order to remov/instal the wing) you'll find that the original audi screws /torx are gonna be seized,damaged,lost etc.
tho back to ur question: I bought a genuine one for a good price, not sure if i would take a risk with some imitation but its all up to you.