I am reading all this with a newly-inspired interest. I recently acquired a full-sus bike that I intend to go trail centering on, as well as seeing how well it deals with local byways and the Ridgeway. I am a full-on SPD convert and use them exclusively on my hardtail and gravel bike. There’s no way I would change this. However the new bike, currently pedal-less, has made me think about what to do. Flats are de riguer for this sort of bike and technical use, and I am willing to give it a go. I wondered about swapping pedals dependent on use - SPDs for local use and flats for trail centre, but I can see this getting tedious if I flip-flop between the two. I’ve never seen pedal that combines SPD with a proper flat platform.
I guess try-it-and-see is the best approach!