I'm with jucius on this one for sure. I also have both these drives, and the liteon doesn't do so well on taiyo yuden t02 media, some scans I get are even worse than jucius's. The nec gets extremely good burns on the same discs, so it's not the medias fault.
My 1633s does like ricohjpnr01 discs (sort of), and I get pretty good scans. But the 3500 still does much better on these discs too. I tried multiple firmwares on the 1633, and the burns still kinda suck.
I also agree with chas0039, just burn on your nec, it's just a better burner than the 1633s. At least for me and many others. 1633s is just for kprobe