Nitrate or celluloïd base has a higher modulus of elasticity than acetate bases have. Comparing equal thicknesses, the nitrate base film is thus stiffer, so to speak. Its index of optical refraction, 1.48, differs only little from that of cellulose acetate, propionate, butyrate, and or mixtures of them. PETP has a typical index of 1.64.
The gelatines settle at around 1.52. Thicker gelatine layers lead to a little more optical acutance (not photographical), a little.
The main difference in their appearance on a cinema screen is — the light. The carbon-arc light got lost in about the same period of time as the industry changed over to safety film, in the 1950s. The first commercial use of Xenon arc bulbs was in 1954 in a German theatre.
Projections with high-intensity carbon arc light and with Xenon enclosed arc light look unlike. The subject penetrates even optics because it was found that the image of the Xenon arc heated up cemented elements of projection lenses to a degree that damages occurred. This led to new designs of lenses. Single free standing elements got preferred back after more than 100 years of optics research. That was only possible with modern multicoating of lens surfaces. Individual elopers due to a projectionist who disassembled a lens for cleaning, I happen to have experienced such things, Petzval type and triplet lenses before WWII and in general of longer focal lengths produced soft-sharp pictures. Xenon light lenses since the 1960s rather produce hard-unsharp pictures. Contrast increased and overall resolution decreased.
On the production side the use of light, the entire lighting concept was also different from what New Cinema, cinéma vérité, la nouvelle vague and other fashions brought. The Ladykillers, the last three-strip Technicolor film, was still lit pre-war style. Lots of light in 1955 and carbon arcs.
To round off my little incomplete survey I must note that only contact positives from original camera negatives are comparable. I saw a fresh print made in 1989 from a 1924 silent in that year. Paris qui dort by Clair, it was mesmerising. The film was shot with, of course, non-coated Tessar-type lenses in Debrie and Eclair cameras, processed most probably by the rack-and-tank method, printed at the time with undertensioned incandescent lamps on Matipo printers or the like. We don’t have the positive stocks of the twenties or thirties any more. On the other hand they haven’t changed so much since 70 years. To celebrate the 200 years jubilee of the French Revolution a number of cinema classics were reprinted and shown internationally.
The light from the glowing limestone is the least known very ingredient of early cinema. The Lumière showed their films with low-intensity carbon arcs. Travelling showmen used limelight. Pictures are still another experience when projected with that light.