Very much like the video tape format battle of the 70s. 9.5mm like BetaMax was arguably the technically superior format, successfully out marketed by the underdog, and in the end completely shouldered out of the market.

9.5mm Pros

Daylight loading film cartridges – yes, tin or bakelite cassettes holding the film that allowed daylight loading in 1932– it was not until 1962 when super8 hit the market that an alternative became available.

Full width film with between the frame sprocket holes (see also 9.5mm cons) – the difference between 8mm and 9.5mm doesn’t sound much, but size is only half the story.

8mm film is actually 16mm film run through the camera twice (once forwards, then a bit like an audio cassette, flipped over and run back the other way). During processing, it’s split down the middle, joined end to end and shown as  8mm film.
So 8mm film is in effect two strips of 8mm film. Each 8mm film has to have a set of sprocket holes along side the image, the frame size of an ‘8mm’ image is 4.5 x 3.3mm

9.5mm film is a single run film and therefore uses the whole width for the image. In addition it puts a sprocket hole between each frame (not along the edge), the frame size of 9.5mm is 8.5 x 6.5mm i.e. 55.25sq mm – but that’s still not the whole answer. The difference of zz square mm means 9.5mm is far more light sensitive, or can be made in far quicker film so is far more able to capture either fast motion, or operate in low light conditions.

9.5mm Cons

Sprocket holes between the frames – can you believe designing something so daft – On a conventional edge sprocketed film, if a hole gets torn, or the pauel gets out of sync, you just rip a few holes.
With 9.5mm film you tear and scratch down the middle of the film frames!

Film recording length – If you want to keep the camera body a comparable size to an 8mm machine, and you need to keep the frame rate i.e. image quality to comparable speeds then if you run the film through the camera only once (rather than twice for 8mm) you end up with rather short run times – A 9.5mm cartridge containing xxm of film last typically 2mins, compared to a dual run 8mm (xxm) giving 5 mins