Don't disagree with the "too many variables" part. Cheap c**p from whatever source will still be cheap c**p. Driving standards vary. etc...
But, my point was, if FIAT thought the standard part would be fine, why would they go to the trouble of designing, manufacturing, fitting, stocking and supplying a different part?
It's a lot of extra cost to do that, from a company that has a track record of using parts from the current parts bin wherever possible.
I personally don't feel comfortable using the "wrong" part just because it fits and is cheaper for me to buy, unless I really understand the implications (so I don't tend to buy cheap c**p from eBay or other sources of random unnamed brands).
But, as I said, just my opinion, and definitely not saying that yours is wrong.
I agree, like for like is best
unfortunately sellers put a premium on substandard parts for higher spec cars like GTI. Often adding Febi or M/M to the advert.
When I last looked a well known online seller was sell cheap knock off arms (not even a correct copy of the casting) with the correct type bush pushed in.
there less compliant to sharpen the steering. Unless your on a race track I doubt there will be much difference and any difference will be less over time.