To make it a litter cleare, here are a few facts:
Fact 1: LG GSA-4120B supports bitsetting which is about changing the "Book Type" of a DVD+R (SL), DVD+R Double Layer, and DVD+RW disk from the original to DVD-ROM because there are DVD-ROM drives and DVD-Video standalone players that can recognize only DVD-ROM, DVD-R, and DVD-RW book types but not DVD+R/+RW booktypes. The firmware must be one of the latest revisions and the burning software also need to be updated. But DVD+RW bitsetting is not included.
Fact 2: LG GSA-4163B supports bitsetting nearly the same way LG GSA-4120B does.
Fact 3: Only bitsetting to DVD+R Double Layer disks is included and it's done automatically without requiring user attention. Bitsetting for DVD+R (SL) and DVD+RW is not included.
Fact 4: Bitsetting for DVD-R and DVD-RW is not possible. Bitsetting is part of the DVD+RW/+R specification.
Fact 5: Most DVD-ROM PC drivies, DVD-Video standalone players, DivX/DVD players, XBox, PS/2, and other DVD-related devices recognize and read DVD+R/DVD+RW disks. Some DVD+RW disks are not made very well and it makes some devices unable to read the disks properly because of the very low reflectivity of DVD+RW, DVD-RW, and CD-RW disks.
Fact 6: Most DVD players can play movies on DVD+R DL disks with booktype changed to DVD-ROM. I don't know if there's a DVD recorder that does not allow booktype on a DVD+R DL disk to be changed to DVD-ROM.