BenQ and NEC are both good burners in their own right. I own both, they both do a fine job.
PI/PIF testing is the disc quality scanning I'm talking about accessible in Nero CD/DVD Speed with the BenQ. The NEC can not do PI/PIF testing of any sort even though people are making attempts to get NEC to add this support to the drive in the future firmware revisions.
Bitsetting is for DVD+R, DVD+RW, and DVD+R9 (Dual-Layer DVD+R's). DVD-R can not use bitsetting. Basically what Bitsetting does is change the format of the written disc from DVD+R, DVD+RW, or DVD+R9 to DVD-ROM. This makes the +R media types more compatible in certain stand-alone players. This mainly effects older units as well as possibly game consoles. The BenQ will do bitsetting out of the box. The NEC needs a modified firmware for this. The firmware my NEC is running is the Mad Dog 2.FA SE firmware which let's the drive enable bitsetting on all those formats.
Really, it's a tough call. I guess I'd just say you'll probably be happy either way - the big thing is pick media that is good from the get go (Taiyo Yuden for instance) and you should be in good shape. The Pioneer, Plextor and new Lite-On drives I really can't give an honest unbiased opinion on because I haven't used those drives.