FWIW, I am back on my FP4 after returning a FP6. The hardware on the 6 is definitely an upgrade but there were some quality control and design issues that were frustrating. Chief among them is the decision to go from a toolless access to the internals to one requiring a screwdriver.
I liked the idea initially as I understand it allowed them to improve the IP rating, but it introduces multiple points of failure, ie. the screws. Iโm sure thereโs going to be people frustrated when they inevitably strip one of these screws and canโt get the back cover reinstalled, but mine came from the factory with two of them stripped.
That is to say nothing about the fact that not everyone has a screwdriver or will carry one with them in case they need to open the phone while away from home.
For my purposes thatโs a fatal flaw I hope they address with a FP7 someday. Until then Iโll stick with my FP4.