Well this is a very broad and 'big' question. There are so many 6SN7 tubes and I've only tried a dozen so far - this being said, it's too early for me to tell which are better, but I am leaning heavily towards the 7193's. Also consider that not there is a great variety of 6SN7 tubes with widely varying sound signatures, and purportedly only 3 types of 7193. But from my impressions so far with testing these 2 types of tubes thoroughly, all tested in good condition, here's how I would personally compare them:
The best of the 6SN7 tubes can be immensely pleasing for an audiophile, even enough so to probably call it their end game. Clear details, great energy / lifelike presentation, musical, good amount of bass (or these variables can change depending on your favorite tube), etc.
The 7193 tubes however, pick up where the 6SN7 tubes left off IMO. The major differences seem to be they are more lifelike / organic (like you "are there" compared to a "simulation" of the music), improved instrument separation, sense of air, and perhaps soundstage as well. Comparing between my favorite 6SN7 and 7193 tubes kept ceasely amazing me: how my ears already told me the 6 was the best, but then with the 7, I was like "no way", this really does sound better: more fluidic, lifelike energy, especially noticeable with well mastered songs (electronic music included) and percussive instruments. There are times however that I actually prefer the 6SN7 tubes because of the different variety of sound signatures they can bring: sometimes I'm listening to an album with too much bass, so I go for one of the 6SN7 tubes that are known to have leaner bass, or if I want a more laid-back sound, etc. Also my 7193's give an audible buzzing sound, which I'll probably have to tone down with an external volume limiter. But these really are amazing chameleons!
