What made you change to a 6SN7 preamp?

@hilde45 another factor in responses so far may also relate to some people jumping up a level or two on design and improved parts quality with their next tube preamp purchase.

Strictly speaking, i.e bumping from something like a $1500 12Axx preamp up to a $3000+ 6SN7 based [a higher quality] tube preamp as a normal course of order.

With that said, I have no desire to change away from my own upgraded 6SN7 tube preamp and particularly so once I heard higher quality n7 tubes in it.

@bigkidz nailed the 6SN7/6922 comparison.

 Perhaps I shouldn't comment, because I've never owned a 6SN7 based pre.  

OK, as long as you insist.  

What I can say is that I've never been satisfied with my system without a 6SN7 tube in there somewhere.  There is just a magic that they impart to the midrange, especially with brass instruments, that has no parallel.  My old Modwright Sony CD player with the right 6SN7 tubes could do French Horns like no other source I ever heard. 

The popularity of this tube has inspired a lot of new production attention.  There are good-really good- new production 6SN7s out there.  They aren't cheap, but they are being produced and they measure up to and arguably exceed many of the top tier NOS tubes.  You can't say that about the 6922.  Good luck trying to find a NOS 6922 that will hold its own against those old Siemens tubes. 

My preamp uses 101D tubes, and I just love the sound of its Psvane WE replica tubes. That tube has similar virtues to a great 300B.  My source uses 6922s, and I sprung for the NOS Siemens tubes which are worth every penny. They are amazing tubes.  Sweet, smooth, great tone, fast and dynamic.  Superb.  I've carefully selected the 6SN7s in my Atma-Sphere M-60's,  I really think all of these tube designs adds something special, and none of them have glaring weaknesses. 

It takes good design/implementation, system synergy. and then finding the optimal tube choice for the equipment you have if you want to maximize performance. 

If I were to move on from my current preamp, I'd probably be looking for a 6SN7 based unit.  

It was a coincidence that my fave little Dennis Had Firebottle tube amp has one 6SN7GTB input tube (only 4 tubes total in that amp including a rectifier and two power tubes), and after using it with a SS preamp for a while I tried a Schiitt Freya (original version) and it has has 4. So now I have a drawer full. The sonic characteristics are simply great tone including exhibiting tonal greatness,  immense personal satisfaction, and impersonal satisfaction. 

nothing at all - no desire to jump on the overpopulated overpriced bandwagon when there are so many lesser known and better alternatives out there.for those that roll their own

In perhaps the past 10 years or so there seem to be more preamps designed around the 6SN7. I’m on my second after using 12AU, AX7’s. I’ll agree with others regarding the tonal quality of these tubes, the spacious soundstaging, and the realistic textures of acoustic instruments. I use NOS exclusively in my preamp and in my amp, which uses six 6SN7s, due to their consistent quality and sonics (when you buy from a trusted dealer). Due to the increased pricing and availability issues of true NOS, I’ve started to take notice of the high quality of new production tubes. Now there will be no shortage of high quality 6SN’s with the availability of new production. For what it's worth, I’ve never owned a new production small signal tube that equaled the SQ of NOS.