Small or big tubes/valves for pre amp ?

Hi guys, have been thinking about going to a tube pre with a solid state amp.

I have a hybrid intergraded amp with small tubes in pre section, I am no expert in tubes, but know my way around the 6DJ8 / 6922 / ECC88 variants where I have preferred the Mullard tubes with my amp.

The pre amp that I have my eye on is the Don Sachs model 2, it uses bigger tubes and I am told that the bigger tubes have better sound than the 6922 variants I am used too.

Would appreciate if someone could enlighten me about the difference in sound signature between these tubes, I believe that Don uses 6SN7 tubes. http://www.dsachsconsulting.com/custom%20line%20stage.html

Thanks!