I am not arguing dB either. I am using dB as a reference. I am discussing specifically high gain wattage also because plenty of 12W Tweeds and AC30s get ridiculously loud.
Those videos are shootouts which is fine. I doubt the differences in frequency response is anything other than measurable low-end and headroom though. Except for the Peavey, I didn't bring that small wattage amp because it's not a great reduction effort IMO. Other brands have done better with modeling pressures upon them.
Anyway, they are not blind challenges. The problem here is identifying in a recording if the guitar tone is 100W or a smaller wattage. That is where the rubber meets the road and I don't think anyone can seriously claim they can call it right all the time in a mix. so the argument becomes a live one and chest thumps and all that to which I replied with the house FRFR coverage. This 100W-only-ism stuff is very niche-specific when it comes down to it.
I think you've hit on the crux of the issue in some ways. I am actually not necessarily saying smaller amps always sound
better than bigger amps. What I am saying is that they absolutely are
different. And it is precisely that difference that makes large and small amps both viable, unique options. One doesn't negate the other, in either direction.
If we were just talking about solid state home stereos or whatever, then I think I would agree with you that as long as you had the same speakers, the watts wouldn't matter as long as you never approached the limits. A 10 watt home stereo would probably sound the same as a 10,000 watt home stereo as long as the speakers were the same and neither system was outputting more than 10 watts at any time.
However, guitar tube amps are different. Everything matters with them, and it is bafflingly difficult to simply "scale down" a 100w amp into an identical version of itself but simply quieter. When it comes to modern high gain amps, I've played just about all of the "mini" versions of all the larger greats. Mini Recto, EVH LBX, Marshall SV20 and SC20, Peavey 5150 MH, Mesa Mark V 25, Mini Invective, Friedman JJ Jr, Bogner 3534, you name it. I actually like a lot of them for what they are, too. However, none of them,
none of them, sound the same as their higher wattage siblings, and it's not just EQ. It's in the response and feel of the amps, the nature of the preamp distortion, the distinct way a 100w poweramp (even when set to low volume) colors the tone in a way that a 15 or 20 watt poweramp simply does not, etc.
I'll also say something else just so you think I'm not biased against small amps altogether. The Matchess DC-30 is 30 watts is one of my all time favorite amps. It's incredible, and it's only 30 watts, and you better believe it can get loud enough to peel paint. However, it's not a modern high gain amp so it doesn't need the girth and hugeness that you can only really get from higher wattage amps.
Do I wish all these mini amps sounded the same as their bigger brothers? Absolutely. Do you know how many more amps I could buy and fit into my studio if the small ones did the job?

They're less expensive, physically smaller, and lighter. What's not to love? But unfortunately, for me, the proof is in the pudding. Every small version of a larger amp I've tried, for me personally, has sounded different than its bigger brother. And I've
tried to make them sound the same. I've put them through reactive loads and applied EQ to the guitar and after the reactive load. It's unfortunately not enough to negate the differences.
Nobody is saying that mini amps are crap. They're not awful. As a matter of fact, in my experience, more often than not they're really good. However, however.... however... however... the 100w versions of those amps are always different in some way besides a simple EQ curve. And that alone means that a guitarist's preference of one over the other is valid and legitimate, because those differences are real and measurable, and the difference is more than can be simply added or subtracted with a parametric EQ.
I'm not even necessarily claiming that the low wattage amps are always better. As a matter of fact I probably couldn't tell in every blind test which amp was the "higher wattage" amp. What I can tell in blind tests, and what most other guitarists with decent monitors could tell, is that more than one amp is being played. I've never heard or played a small wattage amp that sounds identical to its higher wattage version, so there's got to be something to it. That's the only reasonable conclusion I can draw after having played almost all of them.
Is it theoretically possible for a small amp to sound and feel the same as a higher wattage amp at lower volumes? I'm honestly not sure, but I have personally never experienced that and have tried almost all of them.