If you owned a $15,000 all-tube stereo you might notice a difference using so-called "balanced triodes".
Guitar amps? Not so much. Yes, it's snake oil.
All 12AX7s have two sides. The idea behind having those two sides "balanced" is to reduce distortion. There is SO much distortion in any guitar amp pre-amp WAY before the phase inverter that it's ludicrous to think a balanced triode would have any detectable affect.
But, it's a free country, and it's your money, and it's probably only a $20 investment, so why not take the plunge? If it sounds better TO YOU, it makes NO difference what anonymous peoples on the interwebs think anyway, now do it?
BUT, instead of changing ALL the tubes at once, just get a couple and try them in V1. Really, if you can't tell the difference between a $10 tube and a $20 tube, you will have learned a valuable lesson. And possibly saved some money in the process.
I realize everybody desires instant gratification, but if you just change out ALL the 12Ax7s at once, you will have NO idea which tube is doing what and how any replacement is improving your tone, if at all. Tone-chasing takes time. There are no short-cuts.
Contrary to popular belief, pre-amp tubes do NOT wear out at anywhere near the rate that power tubes do, and typically last for many thousands of hours. This is why there is such a market for 40-50 year old Mullards and RCA blackplates.