Why is PDF much larger than PNG for a vector design?
Following Safe size for printing image from browser, I saved my Illustrator file with vector drawings as a PDF. It weighs three times more than the PNG export of the same file at 300 ppi, 4.2 MB versus 1.5 MB. The Illustrator file, saved without the PDF compatible file, is 2.7 MB. Here is the design, saved at 72 ppi: