For 16x high-speed, -R media is often believed to be technically superior due to the lower wobble frequencies (compared to +R) ... the german pc magazine c't believes that the higher wobble frequencies of the +R format affect disc jitter and thus playability on standalone devices and PI-Sum 8.
AFAIK, the wobble frequency is used to modulate the spiral groove so a given drive can extract trhe exact disc position out of the groove modulation.
Personally, I found it easier to find +R media of decent quality than good -R so I bought +R only and set the booktype to "DVD-ROM" to increase playability ... but with Verbatim 16x -R (MID: MCC03RG20) being affordable and widely available, I use these quite often now.
Taiyo Yuden's 8x and 16x -R (MID's: TYG02 & TYG 03) are widely believed to be the best media available at this time ...
Plextor PX-716A 1.05 & Premium 1.06
NEC ND2500A, LG 4163B & LG 8400B (on Reserve)
Plextor PX-116A1 and PX-40TSi (onReserve)
LiteOn LTR-52246S (External) & BenQ DW1620 Pro B7U9
LiteOn SOHD-167T 9S19