It would be slower, I believe CDR drives are limited to 8x speed on USB 1.1. So DVD would be limited to something like .5x speed. You would be better served by buying a $10 USB 2 PCI card.
<A HREF="http://www.cdrinfo.com/Sections/News/Details.asp?RelatedID=4614" target="_new">Here is link</A> to a burner.