If you mainly burn audio, go for the Plextor drives.
If you care more about copying protected discs, the LiteOn is the better choice.
If you still have your SCSI card in your system (I guess so) the 40x SCSI drive may be worth it for you. The advantage, besides the regular SCSI advantages is that you don’t use an IDE channel (if you are low or out of those and you don’t want to buy an additional IDE controller / you don’t have the space for such a controller, the SCSI drive might be good.
I’m about to buy this drive, as I still got quite some SCSI cards/devices and really prefer it above IDE :).
The IDE Plextor will be fine as well… if you got the space on your controller… ofcourse!