Honestly never tried the exact comparisons you're talking about. Always used matched tubes. Well, not always. Occasionally something happens, one goes bad, and instead of swapping out the whole set I run a spare. Over the years this has probably happened a dozen times at least. The spares are never matched, and swapping just one in I've never really noticed a difference. Well maybe its there, just not enough to notice without really trying. And I notice an awful lot of things even without really trying.
So I would put this in the same category as something like bias. If you let your bias wander way off and then dial it in, does that make a difference? I want to say yes. A few times there seemed to be a small barely noticeable improvement in focus or palpable presence. Never easy to quantify such things but I would say its in the same range as cleaning a few (not all, just a few) contacts but less than demagnetizing or even cable dressing if yours are all tangled up on the floor, and certainly way less than putting them up on cable elevators.
So if it was me I'd just buy the tubes, wipe the pins, and call it good.
So I would put this in the same category as something like bias. If you let your bias wander way off and then dial it in, does that make a difference? I want to say yes. A few times there seemed to be a small barely noticeable improvement in focus or palpable presence. Never easy to quantify such things but I would say its in the same range as cleaning a few (not all, just a few) contacts but less than demagnetizing or even cable dressing if yours are all tangled up on the floor, and certainly way less than putting them up on cable elevators.
So if it was me I'd just buy the tubes, wipe the pins, and call it good.