I have had both on my D4. Didn't notice any wind noise with either.
I originally fitted the non-genuine long rails but ended up changing these over to the factory rails, mainly because of the fit in the gutter channel. I was getting pine needles and occasional leaves in the gap and therefore the gutter channel- they hadn't caused a problem but I was worried that they would eventually.
Having now fitted both, the copies are definitely not the OEM LR parts. I had no issues with the strength of them but the differences I noted are:
- paint finish on copies not as good as (powder?) coating or actually probably anodising...? on OEM LR rails;
- fit in gutter nowhere near as snug - the extrusion is smaller (narrower) I think and the rubber seals on the LR rails are shaped to seal;
- rubber strip seal seems to be of a better quality;
- general fit of the feet etc. on the OEM rails is a little better.
David