There's not a big advantage at all. The G*** firmwares only differ from the B*** firmwares by the name. The contents are the same.
However, the B*** firmwares are kept up-to-date.
If you are building production computers, just stick the latest G firmware on the G drive. The especially trouble-free G7P9 is of great convenience for system builders.
If you own the BenQ drive in your own personal computer, then you would want to convert it to a B*** firmware because you get more frequent updates.
For instance, T9, which is not currently available in G*** firmware, fixes data integrity issues with CMC and other medias. It also fixes choppy playback in many medias with many set-top players and/or allows greater success with overspeeding medias to a higher speed.
Although, I usually do not recommend using 16x speeds because 12x is only a few seconds slower and 12x is far better quality. Anyway, B7T9 allows overspeeded discs to play back smoothly on your set-top player. This is not available in G*** firmware today, but G7T9 or similar will be available eventually.
There you have it.
That's why both of the following statements are true:
1. There is absolutely no difference between "B" and "G" firmwares.
2. The "B" firmwares are better.