Using EAC, I actually misplaced my two drives once, repalcing the dead LG with the neweer one... and which ever drive was set to MASTER, was always the preffered EAC choice. Switching them back, the other unit was now the preffered EAC choice... maybe it's more than buffering... I don't know.
I did find that true on one other box I own as well... who ever is set as main/master, gets the nod by EAC.
My notes on the sound of the drives was via USB out to a BC DAC3 and my main system playing one against the other as one might play two CD box players using only one DAC.
I've entirely too much time on my hands. oddly though the ripped tracks do not cary the 'house' sound of the various romdrives...
The NEC Optiarc drive is not among my preffs for anything save DVD making, and due to it's price. ... and it came with the box... the LG firmware update killed it too.
One other thought is ensure the method your pc requires for connectivity.... some Plextor are IDE only... more new pcs are going away from ATA and using ESATA for greater sppeds. With DVD ripping and vurning this is a big deal, for CDs, not so much.