Another consideration is the capstan material, and the tension required on the film to hold traction. If the capstan is the made of the same material as the o-ring, I would agree that more surface requires less force (and tension) which would be preferable.
One aspect where the O-ring may have an advantage is the flexible nature of the material configuration (the O instead of the solid), which may then require less tension over the capstan, but I do not know if that would be the case.
One successful example of stop-motion capstan is the Gugusse Roller built, which uses a large capstan (a skate silicone wheel).
I am doing an iteration of the snailscan, using an aluminum silicone encoder wheel as capstan / driven directly by a geared-stepper.