In SnappyCam, each photo is compressed to a separate JPEG file. There's no inter-frame compression, no motion vectors, etc. The same as mJPEG.
The main differences are:
* Each photo is stored in an individual file. This makes seeking through the living photo blindingly fast. (I guess you could do this with motion JPEG by utilizing an index.)
* Each photo also has full metadata. Try rotating the camera as you shoot. It will follow you. :-) Same goes for the geo-tagging: included are a bunch of timings that aren't normally included, so you can know the "precise" usec when you took the photo.
* Each photo has it's own thumbnail. That allows me to cheat a little bit in the photo viewer: you will see a flash from blurry to clear as you scroll around.
(There are more cheats in the viewer for decoding and downsampling at the same time before you zoom, to make the photo load faster as well. One of the handful of reasons why I rolled my own decoder as well.)