Panasonic DL 4x MEI-T02-001 normally should do better with 4x on a Pioneer S08, perhaps they picked a bad batch for the nifty scans.
Panasonic DL 4x, SONY DL 4x and Taiyo Yuden DL 4x - at least in the 30 pcs spindle from Japan - meanwhile have the same mediacode MEI-T02-001 and are all made by Panasonic.
There are only slight differences in quality, which means: You can go for the cheapest.
Panasonic DL 2x MEI-T01-001 are the best DL media ever for a Pioneer 205 - as You can see in the scans.
You can also find them in SONY DL 2x, the quality is about the same.
I canÂ´t tell, if the Pioneer S08 burns them with the same quality as the Pioneer 205, because I never tried - IÂ´m absolutely satisfied with the results of the Pio 205, so why should I.
You can try BD-R DL 4x with TDK mediacode (TDK, Taiyo Yuden in 25 pcs spindle) or BD-R DL 6x with the Mediacode CMCMAG DI6, but itÂ´s more a hit and miss than with Panasonic BD-R DL media.
I would avoid BD-R DL 6x media for quality reasons.