PIs arent as good as the quality is much poorer
Every set ive seen of them dont lower the car properly, some are lower front, some are lower at the rear, some are even lower to one side, this is all do with not getting the tensile of the spring rate right, this is why they snap
Ive never ever heard of anyone having a Eibach spring snap.
Also, the whole these springs lower xx amount, these lower xx amount never is the truth either.
They'll both probs lower the same at first, however the PI's will probs lower more with time as theyre weaker(giving a poor ride and worse handling over the Eibachs)
And Rowdy's right about the bumpstops, I doubt you'd be able to hit the standard ones with the Eibachs, but with the PI's you probs would, again due to the tensile strength of the spring