It should certainly be interesting. The only real differences between the two stat wise are the seek times and buffer size. The NEC has faster seek times 120 vs 150ms for cd and 140 vs 200ms for DVD, but the Sony has an 8mb buffer as opposed to a 2mb buffer for the NEC.
So the question is which will yield overall better performance? A larger buffer or faster seek. The only other major potential difference I could think of would be to see how picky about media the NEC is over the Sony(Sony does seem to slowly be getting better, however, in terms of media usability however..I'm anxious to hear some brave soul pu tthis new firmware through the ringer to see if its expanded the list of what works).
So, we'll see which turns out to be superior overall, although I'm guessing the more mature Sony drive will probably just edge out the NEC with Sony's larger buffer. The biggest advantage the NEC drive will bring to the table though is providing Sony with its first real competition in the Dual format burning arena. This just means better innovation and better pricing in the long run for us consumers
Competition is good.
All that said, if you are in the market for a dual DVD burner, I'd wait now until the NEC and the new X versions of the Sony drives to both get a full test just to see which will be better and priced better before you buy.