I'd take 8x,
because backups will read better at 8x than at full 12 speed...
that's what I've heard,
but I also heard that an original dvd-drive will lower its speed when read errors occur,
that's why a lower speed won't get you banned (for example a scratched hard to read original disc will be read at a slower speed),
so wouldn't that happen with a backup game as wel? it doesn't read to well at 12x,
won't the drive lower it's speed automatically too?
or does the firmware act differently for backups and originals?
will have to look that one up...