Wow, that’s potentially tough. First step might be to recognize that all the typical issues with power meters (differences between any two devices for one) and the fact that people don’t always perform the same relative to their potential (FTP) on any given day. You more than doubled the difficulty by adding power meters into the mix.
If you have single sided power, you get all the same issues, again doubled. Then there’s the issue of how accurate are either of your FTP’s in the first place. Building on that, each person could be on opposite ends of good/bad days regardless of that info above.
So, I would be extra cautious about taking either value in isolation like normal, not to mention comparing them. I don’t know that it’s at all practical to expect similar, let alone the same effort, even though you are connected on the same bike. We aren’t machines and just connecting like that is no reason to expect similar effort / output, even if you ignore the messy reality hiding in the weeds.
All that ends with a basic suggestion to not put too much faith in those numbers alone. Look at a full picture, like we recommend overall. If either of you honestly feels like there are differences in power production, it may well be down to pure differences in your two bodies and what they excel at or don’t. If you can identify that reasonably well, consider the training that might typically be prescribed to fill that gap.
Probably not much help despite all that typing 
but it seems like a very complex issue to my eyes.