There's no hard evidence to suggest that burning at lower speeds makes any difference to the quality of the finished DVD. There is, however, a difference in the quality of different DVD media. Always use top quality discs such as Taiyo Yuden or similar high end media. Usually anything made in Japan is considered acceptable and stay away from ones that aren't.
There's no preference in DVDSP to change the burn speed but there is in Apple's Disc Utility. Once your DVDSP project is complete, create a disc image and then burn using Disc Utility. If you're not familiar on how to do this check out the article at the llink below:
http://www.kenstone.net/fcp_homepage/image_to_disk_stone.html
- Don
"Please take a moment to fill out your profile, including your computer system and relevant software. Help us help you."
