My goal for my media testing is to include a fair range of discs that people might find, no matter what part of the world they live in. To only test 2 or 3 media types would be very unprofessional in my opinion, not to mention utterly useless to a very large percentage of the people who use the drives I review.
At the very least if I wanted to only include professional level media, I'd have to test Taiyo Yuden, Verbatim, Maxell, Sony, TDK, Fuji, and potentially Mitsui. Including other major brands like Memorex, RiData, and BenQ, is never a bad idea either.
If anything, I'd like to EXPAND my media testing
Punch Cards -> Paper Tape -> Tape Drive -> 8" Floppy Diskette -> 5 1/4" Floppy Diskette -> 3 1/2" "Flippy" Diskette -> CD-R -> DVD±R -> BD-R
The Progression of Computer Media