What made you change to a 6SN7 preamp?

If you made an intentional shift toward a 6SN7-based tube preamp, what sonic characteristics motivated your move?

I have been doing some comparisons and think I have some reasons I like the 6SN7 better, but there are so many factors which could be at play, that I'm not sure what is responsible. 

Rather than list my details for others to analyze, I'd rather hear your answer to the basic question.

Tell me about your path toward a 6SN7 preamp?

What did you change from and why?

Even if, overall, the change was worth it, did you lose anything in the transition? What?