You missed some stuff.
ISU - 90mm @ 90° = 90mm effective
704: 120mm @ 45° = ~170mm effective
Advantage: 704 repels front fire from many tier 7 and 8, ISU cannot repel fire from 6 and 7
ISU - 0.41m BL-10 accuracy
704 - 0.39m BL-10 accuracy
Advantage: 704 more successful in sniper role than ISU
Also, your numbers for the ISU
traverse numbers don't line up with the wiki?