For what I know there are two factors that determine ripping speed:
1) DMA (if DMA is not enabled, ripping speed is very low)
2) firmware. Some drives (both burners and readers) are locked regarding rip speeds.
You can unlock yous liteon 16P9 with omnipatcher (I did it and now I'm able to rip @14x, aka the speed I choose in omnipatcher).
Anyway, there is nothing bad in having more than one drive (I have 5 plugged in my computer right now, 4 burner and a dvd-rom)