Presentations on LibreOffice Draw
Have most of the features you asked: light, easy, align and distribute tools, pictures and master pages.. It does not export/import ppt, but you can copy/paste from LibreOffice Impress that import/export ppt. It does not have onclick animations, however this can be simulated: To simulate onclick animations you can create your final slide. Duplicate it as many times you want and then removing the objects you want to hide from the previous pages. In the end I export the presentation to PDF. This also have some bonuses: draw is very good to make diagrams, it have fluxogram/organogram boxes and connectors ready to use; works on almost any operating system.
Presentations on Libreoffice Write
On libreoffice write you can create page styles with different backgrounds, and paragraph styles called "slide01-title" that insert a page-break with your page style "slide01" and so on. You can also chain the paragraph styles and make very very easy to use templates. For layouting I use tables with no borders. But then you can't export to ppt. For complex images and slides you can use the LibreOffice draw, copy and paste directly in the document.
Which one is best?
I actually use both of them, depending on the kind of presentation I working on. Draw is better for diagrams and drawings and is easier to layout. Write is better for text styles (bullets and so on), to make page templates and allows the presentation be embedded in a regular text document.