Any difference between tubes.

Also some (not all) guitar players want the tube in the amp to distort early or at lower volumes. I would not want that in my amp. That being said some guitar amp tubes I've seen state you can specify when they distort (may be referred to as soft [early distortion] or hard [late distortion] tubes). Those are the only differences I'm aware of.

Many musicians search for NOS tubes to either warm up or put an edge on their amps's sound(tone control-same as, "audiophiles") ie: (http://thetubestore.com/12ax7review.html) and (http://www.guitaramplifierblueprinting.com/Tubeprimerandselection330.pdf)

Yes, ours are more expensive.

Less microphonics? Huh? I've had dozens of various tube guitar amps over the years and, weirdly, it was only sorta recently anybody gave a damn about the brand of tubes...you just wanted it to work! Now I use matched output tubes (biased properly...who knew?), and carefully select the preamp tubes for whatever their job might be. The latest "fadlet" among guitar players is low wattage all tube amps that get the meat out of the output tubes at lower volume levels...a good thing and I'm right there with a 5/15 watt amp. 5 watts can sing...and be surprisingly loud (for the record...I'm currently a 6V6 abuser).

Yes, ours are more expensive.

That has to be the "Gettysburg Address" equivalent! Excellent. :-)