Im going to ad something to my initial comment.
A few Begarices to consider when coming from a pixel 9 in your usecase.
You will get the bewest of android on the picel 9.
You will also get frequent security updates and you will have acces to installing graphene os which is a secure and private operating system. Also in terms of how the hardwear pixel phones are far more secure.
a pixel 9 pro in terms of raw power and raw software is definitly better than the fairphone. Way better camera and way better processor more ram and a usb 3.2 port. Also better screen battery life etc.
however reparebility is comparible worse and the sourcing of the material isn’t as fair as well the fairphone.
also storage upgrading is nonexistant on the pixel 9 pro.
now in terms of privacy.
both come with android althougth the pixel 9 pro comes with a newer version of android.
So yeah google is spying on you ghow ever you can debloat your device with tools like canta etc. (be carefull with that) and revoke permissions on google apps abd olay services. Alternatively you can install custom operating systems that are vased on the abdroid opensource project.
On google you have graphene os, lineage os and e few others and on fairphone you have /e/os, unnoficial lineage and iodeOS and more to come.
Over all graphene OS is the best OS in terms of security and also privacy. It.s much more secure than stock android and far more private so you will be missing out on that option.
The option on fairphone 6 that is even officially sold througth murena is /e/os wich is more private than stock os, but is mediocre overall, especcially when it comes to security, also there was the whole problem with murena silently implementing a speech to text feature that anonimizes user imput and sends it to openAI.
Either way lets sum it up
Getting a fairphone 6 from a pixel 9 pro is definitly a downgrade. However if you don’t mind loosing preformance and security aswell as really good canera quality, while getting a really good fingerprint reader, almost perfect reparebility, A microSD card slot and a cool switch on the side. Then sure go for it, but be realistic the fairphone 6 is not a flagship and more or less a midranfe phone from a few years back, however with better working conditions and fairer materials.
Ultimatly its your choice.
I would stick with the pixel and let the fairphone 6 mature a few years and see how they handle software updates etc.
Good luck either way and I hope you find the right phone for you