More facebook/instagram ad types (Formats)
More ad types like images, posts, videos..stories etc. not limiting to only URL ads
Get warned about most policy violations even before submitting to an ad platform. When using your own ad accounts, this feature will reduce your risk of getting suspended.
Google Ads Site Extensions
I know Ad Extensions has been mentioned but Call Outs, Site Links and Rich Snippets would be really helpful
Adding the Facebook Pixel
Using the Facebook Pixel in Balloonary ad campaigns for building audiences and running remarking campaigns