Both drives have their merits. For reading all discs, and writing DVD+R media at 16x, the Plextor 740 is the clear leader. However, the Plextor was poor at writing to the DVD+R DL media, and DVD+RW. Notice, I did not award Plextor's drive the "LD Approved" designation. The LiteOn, while having issues at max write speeds, was a more balanced, although slower drive.
I'll try to do the scans at 4x next time, although it's only an 8x reader so there shouldn't be much difference.
LiteOn 1693S review
Plextor 740A review
BTC DVDRW 1008