Whose assets are better - Illustrator or InDesign?

I'll try to be brief. 

I'm trying to save the smallest file sized assets to be used for e-books and other applications.

I created my art in Illustrator and scaled them to fit a "phone" format in InDesign.

I would like to export them using Illustrator, so I could save my assets in varing files and sizes, I'm trying to make my files small as possible, for web applications, while at the same time, have larger files for printing. I want to have my cake and eat it too.

Here's my question ... since I scaled the artwork to fit an InDesign format, do I need to copy and paste the sized InDesign artwork into a new Illustrator file, to have the smallest asset file(s) size(s), and then save my assets or can I save my assets directly from InDesign?

As far as I can tell, InDesign does not give you the flexability that Illustrator does.

This is for a series of paper folding e-books, that uses a standard 8-1/2" x 11" as a base for multiple projects, that will hopfully will change the world for the better.

Any suggestions will be appreciated.

Thanks, John