In the past, it was practical and preferred to export from iMovie using QuickTime prior to making a DVD with iDVD.
The resulting video file would be quite useful to have as a high quality h.264 MOV backup copy of your video.
It also would make it possible for the video to be played directly from a file, skipping the DVD.
Having iMovie projects as multiple exported video files also made it very convenient to combine multiple videos or clips on a single DVD.
Exporting with QuickTime (Share > Export Using QuickTime…) with the Use option set to LAN/Intranet produces good results. It’s necessary to modify the Options to ensure the video dimensions are the same as your current project and not reduced unnecessarily to 640×480 (do this under Options > Size).However, at some point along the way, perhaps due to an update in iMovie ’11 or QuickTime, the export process began to take a very long time. For example, a 90 minute video might take 5 hours to export with QuickTime. By contrast, when using the iMovie option to Share to iDVD (found under the Share menu), the export time would be 50 minutes instead of an estimated 5 hours. These export times are based on using a Mac Pro with two 2.26 Quad-Core Intel Xeon processors and 12 GB of 1066 MHz DDR3 RAM. So, it’s likely your wait times would be significantly longer.
As a result, for projects where you want to put a single video or clip (iMovie Project) onto a DVD, the most expedient method is to use the Share to iDVD option.
Other than the time savings, this option really isn’t very good.
For example, a video shared to iDVD with multiple chapter markers will automatically choose a theme for you, and create the sub-menus for scene selection. You’ll need to manually fix each one of these sub-menus to match your desired theme.
If, instead, you had exported using QuickTime, you could have started iDVD manually, and selected a theme prior to dragging the multi-chapter video into your DVD. In doing this, the selected theme is automatically replicated in sub-menus saving time and also optimizing sub-menu lists.
These are a few considerations to have in mind prior to making a DVD from iMovie.