That depends on the footage. Is it SD or HD? Is it 4:3 or 16:9?
Have not get any good results with sending it to iDVD? Have you made some tests on how different settings (there aren't much anyway) result in different visible image quality?
What about creating a new iMovie project and then importing the finished sequences from the other projects? You might have to export the finished sequences first as a QuickTime (.mov) with the AIC codec first in those other projects and then import them (via the Move option maybe, to safe some time) into that new project.