Now you know that -R is EXtremely BAD ! ! !
-R 無法16X燒 ( almost a Golden Rule ! )
-R has more difficulties to reach high speed than +R !

So, the machine +R片優 is very important , and 燒片可測分 is the most important of ALL ! ! !
For you can verify your DVD quality by Bq 1640 測分 function.

Remember, the LF function of Fake 4551a is not meaningful to most users,
BUT 燒片可測分 is meaningful and very very important ! ! !
Though my DVD G is NEC 3550a , but I never modify it even upGrade the firmware by J大's great 3550a / 455x bin files.

My suggestion is Bq 1640 ! ! !

+R is superior to -R ( result from the different Addr_Info Carrying Method of them )
-R's Addr_Info is carried by the Land Pre-Pits while +R is carried by Phase Modulation Wobble.
-R has worse noise immunity and more error prone . . .