Here's a little bit more information to help you decide which to use :
Some movies have a kind of region protection which will detect if the player playing it is RPC1. If it is, the disc will refuse to play. I have not encountered this before and have only read about it. I doubt that it is commonly used. Still, if you mainly use your DVD writer to watch movies, and you want to make absolutely sure every movie will play on it, then you probably want the auto-reset firmware, which shows up as RPC2.
Some DVD ripping programs such as DVD Decrypter, have a bit of difficulty breaking the encryption on discs if the DVD drive you are ripping from is RPC2. It does not have that problem with RPC1 drives though. So if you happen to use your drive to rip DVDs quite a bit, you might want to use the RPC1 firmware.
This is what I know so far anyway. Corrections, comments, etc are welcome.