Sony contracts junk for their media. Look for verbatim (made in signapore on the label, 8x write speed) or all else failing anything with a Ritek media code (Fuji comes to mind, though they are hit and miss from batch to batch like sony, memorex and many other brands.) It also really depends on whether your burner supports the specific media code (if not check for updates else you will only get coasters when burning at the layer break).
Also, burn slow unless you know your burner performs better at a higher speed. 2.4x may take a while, but most burners burn better at that speed.
BTW: -R DL exist, but are not very well supported by any of the burner manufacturers and thus are essentially junk to most burners/readers.