Flash Builder vs FlashDevelop

I'm deciding whether to purchase Adobe Creative Cloud to use Flash Builder, or if just to use FlashDevelop instead (which is free) to develop Flash Games. Can FlashDevelop do everything Flash Builder can do, including producing AIR content, iOS content, and 3D content? What are the limitations that FlashDevelop has? There must be a reason it's free and Flash Builder is paid for.

Thanks!