The 111D; it kicks butt.
The Lite-On is not a very impressive burner, IMHO. The 111Ds burn quality smokes it. But the Litey can do media tests, too...which is why I have both.
I've been less than impressed with the 18x Samsungs. I had the non-lightscribe drive, and it was pretty darn good except for one odd bug. So, I replaced it with the Lightscribe version. Burn quality is overall pretty horrible with it. I'm tempted to try again on a non-LS model, but think I'll just wait for the 18x LG drive.
Newegg has the 18x Sony and NEC drives now. I'd like to see a review of those things writing quality before I can comment.
BenQ 1655, BenQ 1620, LG 4167, Plex PX-716SA, Samsung SH-S162L, SH-S182M, Pioneer 111D, Lite-On SHM-165H6S and 1.9TB of HDDs to feed 'em and an X2/4800 to crunch for 'em.