Question for all tape traders out there (non-U2 content)

In all the tape trading site, why do all traders require either a
Maxell XL II, or TDK SA (or SA-X)?

What's wrong with other type II, high position, chrome tapes from
reputable companies like Sony (their UX tape) or even Phillips (which
makes really great tapes at a more affordable price)?

Aren't they all supposed to have the same quality and sound the same
(given that they're all from reputable companies and not 'generic'
brands)?

Thanks in advance!

Cheers,

J

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