Formatting DVD Speeds Between Three Macs

I did a test to see which of three Macs would format a DVD-RW the fastest. The DVDs formatted were Sony brand using Disk Utility.

I didn't time them, just went by which computer was the fastest. Three computers were a 2.4 Black MacBook with the factory Matshita drive 2GB ram, Mac Pro 2.8 with the factory Optiarc DVD drive and 2GB ram, iMac 2.2 with default Matshita drive and 3GB ram.

The Black MacBook was the clear winner. iMac second place.

Anyone have any ideas or observations why? To me it looks like the Matshita drives are much faster.