The same question also applies to "how is WebEngage survey different from Qualaroo?"
Here's how we present our case:
1. WebEngage products can be "targeted" at certain audience segments based on a lot on in-built criterion like URL patterns, geography, cookies, traffic source etc - http://webengage.com/survey#targeting
3. WebEngage works via a JS widget code which is a one-time integration. All knobs and controls sit in the WebEngage Dashboard and for any new notifications or surveys that need to be run, customers don't need to change any code on their website.
Well, so you are able to create notifications from your twitter/fb/linkedin etc. Few use-cases are well discussed in the post and I am sure their are many more.
Also, it mentions "We’ll be adding complete customization capabilities (colors, targeting etc) to Notification." So there is going to be a layer of targeting. (see this http://webengage.com/features/survey-and-lead-generation | first para talks about targeting)
Analytics around notification displays, clicks etc are going to be very insightful, I am sure.