I'll give you one comparison where the 7800 won: Ballblazer 7800 versus Space Football SNES. It amazed me that BB, which was made years earlier on the technically weaker system, was soo much smoother and more enjoyable than Space Football.
Fun Fact: My review of Space Football ended up getting quoted in The SNES Omnibus Vol 2. Yup, in a strange way, it's my fault that the 7800 got mentioned in a book about the SNES!
BTW, from my experience, I believe that two things killed the 7800.
1) The sale of Atari in 84, which shelved the system until 86. instead of coming out before the NES, it came out after.
2) The lack of NES style games in it's prime. They started with arcade ports, that although good ports, the games were starting to feel a bit old and tired to the general public. Then they ported computer games that didn't appeal to the general public (Ace of Aces, Fight Night, Impossible Mission). It got some NES style games at the end of it's life (Midnight Mutants, Ninja Golf & Alien Brigade were all excellent), but by then the 16 bit era was beginning and it was too late.
However, saying killed is a little much. The system had a solid life, decent size library, and was able to outsell the Master System in the States during it's prime.