"The Best" one to use will always be the one that delivers the results you want. In most cases, the stock firmware is the best for quality and reliability. If you're not comfortable with flashing back and forth between versions, and if you are not willing to void your warranty, then stick with the stock F/W.
Different drives of the same model do not all respond the same to different F/W and media. You really have to evaluate them for yourself using your own drive and media.