is a post with some measurements of transfer rates to and from an external enclosure using various interfaces. The device inside the enclosure was a hard drive rather than a DVD drive, but you can still see that FireWire is capable of supporting the ~21 MB/sec transfer rate needed for 16x recording.
Whether or not your system as whole is capable of 16x burning through an external enclosure is another question. That would depend on the particular enclosure, interface cards, etc. you use. It safe to say, though, that you will have a greater chance of success with FireWire than USB 2.0.