In my opinion:
Form: great, native, missing features, not that intuitive, not that many shortcuts
Origami: great, native, intuitive, a lot of timesaving shortcuts, the only downside is an outdated QC and performance decreasing as the prototypes get complex (same case with any other tool really)
Framer: not native, requires coding, can get complex, not that easy to use
Pirate: not native, buggy webapp
Proto.io: not native, buggy webapp
Just curious; is being native a key feature?
Yes. Definitively. If you want to prototype a realistic interactions and get the real feeling of them.
That video was awful