I agree with Jsc... it would all be about driver skill in identically prepped cars with Eibach vs. H&R/Neuspeed...

I loved the "my friend with so and so parts would whoop you" thing though...I hear that from time to time...I won't say anymore about that.

As far as the springs go though... It would be all about the springrates.

Honestly I've never done a lot of research into Eibach's spring design...i have heard that the Pro-kits have identical springrates to Sportlines just less of a drop. I DO know that both Sportlines and Pro-Kits are progressive rated springs just like H&R/Neuspeed Sports. That kind of setup is aimed more at ride comfort than pure handling performance.

Whereas Neupseed/H&R Race springs are linear rated springs...

Just in my experience I'd take a linear rate spring over a progressive spring anyday. But my main goal is handling and not just looks...
So choose accordingly depending on your goals. There's nothing wrong with either...you just have to make certain decisions and accept certain sacrifices depending on which direction you are heading with your car....