>>212116566Back in the day 70mm had 4-track stereo while 35mm had only stereo, but nowadays this is irrelevant.
70mm has a native aspect ratio of 2.20:1 which is slightly less wide than anamorphic (=cinemascope) 35mm at 2.35:1. However Ultra Panavision or MGM Camera 65 (same thing on a technical level) was 70mm with a 1.25x anamorphic lens, resulting in the even wider 2.76:1 aspect ratio, but this was only used for a handful of films including Ben-Hur, the last one in 1969 iirc until Tarantula revived the format for Hateful Eight.
The larger negative area of 70mm is really quite noticeable and can look gorgeous; I've seen 70mm prints of Lawrence of Arabia and 2001 and it's really impressive cinematography.