discussion reminds me of Advanced Photo System in film.
In addition to the differences that Bernard mentions, there is another huge one: 35mm film had such huge usage and economies of scale that there was no cost advantage to any smaller film format (printing costs exceeded the costs of 35mm film and development), and neither APS film nor cameras ever had a cost advantage. Also, the compacts did not have a significant size advantage, once 35mm camera took the stratwgy of offering lenses with the same FOV coverage of about tue same soze, through having longer focal lengths but about the same sized lens elements, which meant increasing minimum f-stop by about one stop, which was easily compensaed for by using 35mm film about one stop faster, with the larger formats and smaller degree of enlargement needed offsetting any image degradation. ISO 400 and 800 films became the standard choice form many of those cameras.
Despite over a decade of predictions, this strategy has not at all lead to 35mm format dispacing the smaller formats in digital cameras, because the very large cost difference persists. Even the latest $2000 bodies cost many time more than entry-level cameras in the smaller formats, and as much as the top of the line Canon and Nikon film SLRs did.
Another difference is that the smaller formats persist in offering dostinctly higher sensor reolution (lines per mm, pixel spacing) so that unlike woth film, 35mm format cannot duplicae the results of the smaller formats by using the same focal length and then cropping. This lp/mm resolution gap shows no sign of diminishing.
