When my client desires a DVD, my habit has always been to share my PRE7 HD timeline as Share>Disc>Burn to Folder and then burn the DVD from the folder.
When I was trying out DVD AS, I followed Steve's instruction to put out the timeline as an NTSC file, but I always made sure that it was at best quality. Subsequently, I learned that the best quality NTSC file gives the same quality DVD as one burned from a folder.
Today, I burned my PRE7 HD timeline directly to disc, once for the DVD and once more for the Blu-ray (the only way to get a Blu-ray with PRE7). My intention was that I would then use the discs to create ISO image files with ImgBurn.
Whoa!
The DVD burned directly from the timeline is not even in the same ball park as one burned from a folder, in terms of quality. It's as if the video was made through a diffuson lens--just like in the old days, when I would output my PSE slide shows to a WMV file and then burn the DVD from the WMV file.
Additonal advantage of burning to folder before burning the first disc: If the client later asks for more copies of the DVD, it's easy to burn them quickly from that folder.
P.S. Is anyone aware of a good reason to also create an ISO file from either 1) a disc that has been burned from folder or 2) the folder itself (which ImgBurn is capable of doing)?