for what you want, i just can tell that the nec3520 is ok.
Maybe not the best "burn quality", but perfectly readable by everything.
about the dvr-109, just be aware that there will be problems if you try some xbox backup
with the benq i read some people having troubles with ps2 backup, nothing perfectly clear about that, so i'll stay away from this one for ps2, even if this one is supposed to have the best "burn quality". It may or may not work with ps2, it is a risk.
bitsetting is a feature on dvd burner that allow to flag DVD+R / +RW or dual layer +R as -R, or something like that, so that there is more compatibility with home dvd reader or other stuff that usually reads -R. The Dvr-109 does not have this feature.
PI error => we enter the realm of "burn quality", .. you should parse forums for that. Know that a burned dvd can have more or less PI errors depending on the media and the burner, but can still be perfectly readable (unless the number of error is too high).