There seems to be a lot of questions regarding the 3S firmwares and which one to use... so...
- BS0x (e.g., BS0K, BS0R, BS0S, etc.)
These are 1633S firmwares with 8x -R using ZCLV. These firmwares are the most well-developed and mature of the 3S firmwares, but have slow -R (8x, compounded with ZCLV).
- CS0x (e.g., CS02, CS07, CS09, etc.)
These are 1653S firmwares with 12x -R using PCAV. These firmwares are newer, which may be a mixed blessing. Some claim that the -R write quality has dramatically improved with the new CS0x firmwares (a good thing about being new). And there are scattered reports of -R leadin problems (a possible bug in the firmwares? ) (a not-so-good thing about being new). These firmwares contain some significant changes over the BS0x firmwares and people seem to have mixed results (some say it's much better than BS0x, some say it's worse).
Although these are nominally 1633S firmwares, these are really 1653S firmwares. They are essentially CS0x firmwares with a different drive name. That's it. It would seem that the BS4x firmwares are really identical to the CS0x firmwares. So you should NOT compare these firmwares to BS0x, but instead, they should be though of as CS0x firmwares.
If you have any tests or experiences of BS0x vs. CS0x/BS4x, please post them in this thread.