Ninja is really marketable. He has merchandise sitting in Walmart, was on big tv shows like Ellen or hosting a NYC New Years Event.
He's the face of gaming for all the non-gamers right now.
Shroud is just a very good gamer and has a big audience, he's not that marketable compared but still worth a decent penny I guess. He's probably considered the best FPS streamer out there whenever a new game comes out. He's the go to for many.