The DVD burners in the iMac (8X write speed for DVD±R) and the Mac Pro (16X write speed for DVD±R) aren't the fastest on the market. There's actually a mechanism created by Samsung that can write DVD±R at 20X, and it's found in OWC's Mercury Pro DVD-/+RW Samsung Super Writemaster 20X External DVD burner.
Stories by Jeffy Milstead
Even if you have a Mac with a dual-layer DVD burner, there are good reasons for buying a newer external burner. For example, MacBook users might be fed up with the pokey performance of the MacBook's built-in 8x burner. A burner like LaCie's d2 DVD±RW with LightScribe can burn some single-layer DVD±R discs at 20x-a huge boost over 8x speed. However, if you plan on using the d2's LightScribe feature to etch custom disc labels, be warned that any gains in burning speed will be more than offset by the 15 to 30 minutes needed for etching.