I’ve got both phones (started with the pinephone). The Pinephone is a good thing to test, develop, try.
Compared to the Librem5 the Pinephone (running mobian) is slow up to the point of unusable. The Librem5 has got a way better touch screen: it’s responsive whereas my pinephone needs special care using the touch screen.
Furthermore: Paying for the Librem5 you also pay for development. For the pinephone you pay for the hardware (yes, sure, some money went from pine64 to developers).
The pinephone is more or less like a sbc (like raspberry pi or rock64): you’ve got to know what you do and how to help yourself. You’re depending on the great and very supporting community and you’re not a customer. You’re just another user.
The Librem5 is meant to be a product - a working combination of hardware and software. The great and very supporting community around linux mobile phones is very supporting and in the end if a problem can’t get solved you can rely on the great staff of Purism to support you.
As much as both - pinephone and Librem5 - have there place and are pushing the linux mobile phone ecosystem ahead they differ much in philosophy.
If you want to try and do not have the money or the patience to buy a Librem5 go ahead with a Pinephone and probably soon with a Pinephone Pro. You’ll give back to the community and you support the ecosystem.
If you have the money, if you’d like to have a product inlcuding hard- and software and if you’re willing to support the new ecosystem and the development: go for a Librem5.
If both applies: get both 
.