Here is a post comparing the specs of Librem 5 and PinePhone: https://forums.puri.sm/t/comparing-specs-of-upcoming-linux-p... (with a link to a comparison of 12 phones).

Most notably, Librem 5 does not have a GPU designed in 2008, DDR4 Ram and likely has a faster eMMC, which is not too fast on the PinePhone either. However, the main issue with the PinePhone imho is that it does not have a larger battery that would help avoiding all the daily problems with deep sleep.

I am going to compare the two phones once I receive my October 2017 Librem 5 preorder on my blog (https://linmob.net) and my video channels.