According to Aopen's specs, there's no BURN-Proof listed. I'd guess the 4MB buffer is there to address that problem, at least partially. I don't believe Teac's 12/10/32 drive has it either.
For the price difference, the Plextor is definitely a better deal. You'll find extremely few Plextor owners that are dissatisfied, and for that matter most are Plextor fanatics. My first Plextor was a 2.2x SCSI CD-ROM drive that still works just fine, and I've been using them ever since. A bunch of us are still waiting for Plextor's first DVD drive.
Also, if you're doing DAE, once you've used a Plextor you ain't going back to anything else.