I can't comment on the Asus, I can assure you that ATA33, ATA66, and ATA100 doesn't make any difference for DVD-ROms. Anyway, here's my experience:
Pioneer 106S/AOpen DVD-1640ProA
Pros:
Slot load
Good CD-ROM and DVD-ROM performance
Not too loud
Cons:
CD audio ripping locked at 16x
DVD movie playback/ripping only ~8x average
No sub-channel reading, not the best for CloneCD
Lite-On LTD163
Pros:
Very affordable
Best overall CD-ROM and DVD-ROM performance
Great ripping speeds in CD audio and DVD movies
Cons:
Reads CD-RWs rather slowly
Doesn't handle ill-maintained CDs too well
Somwhat loud
Toshiba SD-M1612
Pros:
Cheap
Very good CD-ROM and DVD-ROM performance
Reads CD-RWs extremely well
CloneCD's favorite
Quiet
Cons:
DVD movie playback/ripping locked at 2-4x
No headphone jack and volunm control on the bezel
No DVD-ROM is perfect, in fact, they're all far from perfect; every major brand has at least one drawback, you really have to decide what's important and unimportant to you when choosing a DVD-ROM. It's pretty easy to figure out, if you just want the absolute best performance in almost every category, go for the Lite-On. If you use CloneCD a lot and don't care about DVD ripping speed, then go with the Toshiba. Pioneer/AOpen doesnt have much going for it, but it's the only slot load DVD drive.