I have always used .009s for regular e-e tuning on guitars with 25.5" necks and. 010s on 24-3/4". That gives about the same tension when swapping back and forth between different guitars. The exception is for 60's-style instrumental music for which I prefer heavier strings. Rick Beato's test unfortunately ignore both clean sound and sustain. With distortion and/or effects masking the true sound of the guitar you can get almost any result you want with any string gauge given a few minor EQ tweaks.
Indeed, that youtube test is whack imo. Your attack eventually adapts to the gauge you use, of course if you attack the same way on .012 that you do on .009, it'll sound like you don't pick hard enough and if you attack like Stevie Ray Vaughn on a set of .009, it'll choke and sounds like you have no control. Also, as heldal said, this riff he does and overdrive he uses is quite useless to compare tonal difference. The biggest thing about string gauge which he doesn't seem to address is that feel, stability and sustain is a much greater variable than tone in my opinion and except maybe
for the latter, those can't be understood by a youtube video.