I'm making a DVD of a dance recital (yeow!) and I have 2 acts, each with 25 individual dances that I want the parents of the children to be able to navigate to with button. Each act is an hour long. Is it more efficient to place each entire act on a timeline and navigate via chapter points, or have each individual dance on it's own timeline and navigate that way.
It depends on how you want the user to be able to navigate the DVD. It's not really a matter of efficiency. (Well, it's far easier to manage chapters than multiple timelines, but I assume you're asking about the user's experience.)
Do you want the users to have the option to watch the whole act or to watch each dance individually, and then have the DVD return to the menu afterwards? If yes, each dance needs to go in it's own timeline. Then set up the acts using a playlist.
If you don't need that, and just want to have chapters for each act, then just put each act into it's own timeline and place chapter poitns on each dance. This usually more intuitive for you and the user, the downside being that you have to use that pesky "menu" button on the remote if you want to get back to the menu after watching any particular chapter. ;)