Which Preamp Tube is most consequential: Input or Gain


I've just gotten a pair of 1950s Tung-Sols for my Schiit Freya to replace two of the stock Russian NOS 6SN7. I will try them in both positions, but is there a typical position of more impact in terms of rolling preamp tubes in the input vs. gain positions? Thanks for any experience you'd like to share.
peterf6
Thanks, @lowrider57 , the Freya has two tubes per channel. Forward and rear are L/R channels; while the two left tubes are Input and two rights are Cathode follower. So I've been changing the two inputs or the two outputs to keep the channels the same.
@peterf6 , ok thanks for your comments. That’s a different layout than preamps I’ve owned. Typically, tube circuit is L R in front. 
And of course, Ralph (atmasphere) is correct.


@atmasphere and @lowrider57 Thanks for that. I know zilch about preamp design despite having tube gear for 40+ years. Isn't the input side a balancing and follower for gain? Why is the input the place to start? I'm seeing it play out in my roll, but curious...