If I layout the same design in Illustrator AND InDesign, Illustrator will always have a ridiculously higher file size. InDesign will produce a print-ready PDF at 9 megs, and Illustrator will produce one that is 34 megs which can't be sent by email. I've tried rasterizing photos and cropping them but this is a rather arduous process and has resulted in a lot of errors as the rasterize process isn't great either.