Video Presentation software - Keynote vs QT vs NeoOffice vs. . . .

1) Would using Keynote give significant advantages over QT for doing video presentations? If so, what are they?

4) I'm sure presentations with video would work with my imac, but what about an old G-3 laptop 800?

5) Anyone have any experience doing presentations with NeoOffice or OpenOffice? Any disadvantages compared with Keynote?