Music compilation encodes only one frame, not matter how long the video lasts on the screen. Very efficient, but obviously you cannot have any movement. A picture compilation actually creates real video from the picture. By "real" video I mean that it creates 24, 25, or 30 frames for each second of running time. This permits movement. This also means that it will take up a lot of space.

If all you need is still photos, and you don't need to vary the time they are on screen, you can put a LOT of still photos onto a DVD using Music Compilation. I do this all the time as an "extras" option, especially when I have some event, and everyone contributes still photos. I put the video of the event on the DVD in the usual way; I put the still photos in their original format in an "extras" folder that can only be read when the disc is put into a computer; and for those who don't have a computer, I add the Music Compilation with all the photos. This last item only adds a few megabytes to the project, even with hundreds and hundreds of photos.