Are you sure about this? As an example, here are the specs of Toshiba's current top of the line DVD writers, taken straight from their home pages:
SD-R5372 (desktop): 5x DL DVD+R; 16x DVD+R; 12/16x DVD-R; 4x DVD-RW/+RW
SD-R6472 (slimline): 24x CD-R; 10x CD-RW; 8x DVD-R/+R; 4x DVD-RW/+RW
So the slimline is already quite a bit slower at writing DVD-R. I don't see why this should be a direct consequence of their construction, so they do appear to be different. Of course, for copy protections what matters is that they both use the same chipset, and I suppose that is not unlikely given they both come from the same manufacturer.
Anyway, but if someone had some first-hand experience on either of these drives that would be perfect. Thanks!