We must be careful comparing apples and oranges, or Teensies and Photons.
I havnt tried the Photons, BUT in a thread devoted to the question of accessing every single pin in a 48 pin formfactor and probaly use every ounce of cycles the core cand deliver, a CM3 that uses a fair amount of resources and pins for talking to a wifi chip, well ... to me that sounds like the answer to a different set of requirements.
Reading a lot of the chat on formfactors, pinouts, and ++'s and devtools all I can say it depends, depends on your background, the size of your projects, if cmd line tools feels homely and right or scary and arcane. If you prefer the small size, fairly complete set of easily useable libraries in a basic GUI that gets .... annoying ... as the project gets large, or you want a platform with everything available, until you start ranting how obscure Eclipse is. Personally I do projects that benefits from processor speed, memory but not a huge amount of pins.
Its all compromises, we live with them and no chise will ever be perfect.