As an owner of an FP3, here's my verdict

My device came with stock android, rooted it to get back functionality that Google has ripped out of newer Android releases (including app backup/restore & call recording). My previous device was an S5.

• FP3 feels good to hold, but it's made out of recycled plastics so expect the matte body to turn shiny after a couple years
• Quite expensive for what it is
• Stock camera software is 💩, grab a copy of Gcam or OpenCamera for a much nicer experience
• Headphone jack
• Replaceable battery
• USB C port is wired for USB 2.0, so no displayport functionality here
• Loud side firing speaker (on left of display)
• Very active forums. If you have issues, they are usually resolved in the following system update, as long as a FP employee comes across the thread
• Charging speed is configurable if you're rooted. Max speed configured from the factory is 14W, I've changed mine to 2.5W
• Updates do take a loooong time to be released, as FP is supporting the device outside of the Qualcomm's support period
• Good availability of replacement parts and fast delivery

As for reasons to really get this device? Not many IMO. Compared to a pixel, it boils down to the FP being more expensive, being manufactured "sustainably" (via agreements for workers to be paid more, using recycled plastics etc), modular replaceable parts (incl battery), being a reasonably transparent company (if you interact with them via forums - the marketing team seems to like greenwashing so I mostly ignore their stances), and support for quite a few ROMs, as well as entirely replacing Android with a full Linux OS.

I wish the same product manager that designed the FP3 stayed with the company, because it's a very nice looking device for what it is, and very well thought out, even if the software can be a bit meh sometimes. The FP4 seems like a less-than-ideal direction IMO, and feature-wise distinguishes itself less from generic mainstream devices compared to the FP3.

Personally I don't think i'll be getting another FP (Or another mobile device in general?) anytime soon.

From a software perspective, go get yourself a Pixel and flash GrapheneOS! From a Hardware perspective, the FP would be the longer lasting option IMO. If you're happy with your current device though, give "Capitalism" the middle finger and keep using it.