Both, you must mix and match to keep the consumer guessing.. It sucks to just use one method and beat it into the the prospect.. I currently use Urban Airship and a smaller entity for these type of messaging.. My. Most viral and highest ctr were a mixture of push notifications that lead to media within app that where content gated and once unlocked released not only the media, but also a coupon.. You could update the coupon with a serial number that these pushes would provide.. #SecretSauce