That's your system and your findings that is fine but peoples findings on Mullards are as I've described, I had a possession of over 30 Mullards various kinds for the 12AU7's integrated/headphone and preamp's I have they all sound distinctively close to each other.
Baldwin organ tubes 12AU7 are made by Sylvania.
The best Mullards are Holland and Blackburn plant, same two plants Amperexes come from.
LOL, Telefunken's are not rolled off period that award goes to the English plant make Amperex's dark and laid back sounding, you must have a rebrand from another manufacturer, there is a reason they are the best amongst the dual triode family with a strong following out there, best 12AU7 based tube money can buy for sound is the ECC802S, made in West Germany. There lower "generic" range that go for $40-100 fitting the usual description of smooth ribbed plates and a D getter blow Genalex ECC82's out of the water (which are also good tubes) that go alot more.
People ? which people ? Not the ones I know. I have a ton of 12AU7's and 12AX7's (every type, 5751, WA, JG, A's) and have tried on a variety of systems. Even self built. Black plates, triple MICA. So that's YOUR system and YOUR findings and YOUR preference.
One thing I have found out about tubes. You can't label a set or type of tubes as "the tubes". You also cannot discount tubes or assume (as WAY too many people do here) that they must be fakes. All tube preferences are system specific, application specific. They also have to be matched to the links in the chain. So if you have a tube phono stage, tube pre and tube amp, it is much harder to balance than just one of those having tubes.
In my power amp, I tried every 12AX7 pair from $10 to over $125 a tube. The final one ? A very rare and hard to find pair of Sylvania 5751 Triple Mica Blackplates Yellow print. why ? detail. My system is very detailed with forward mids, nice tight strong base, wide soundstage. GE and RCA's had the detail, didn't have the forward mids. On my systems, Tele's are DULL. Mullards are sweet (#2). Amperex. yuck ptooy.
Bottom line, don't disparage. encourage. If they want to try a Mullard it may be the most incredible tube they one...or ..they may hate it...only their system and their ears will know.