There's also the issue with embedded fonts. Acrobat can subset glyphs from a font for PDF files, whereas ePub files will contain the entire font. This means that if you're only using one character from a 600 KB font file, the entire font file will be embedded, where it would only take 6-10 KB in a subset. And if you use 10 different 600 KB font families... You get the idea.
But in general, images usually take up the most amount of space.
Last edited by DSpider; 01-02-2013 at 08:50 AM.