It's actually quite fascinating. This is a culturally very significant moment. This is basically the official changing of the guard. Grime has now been consumed by the larger UK rap, and by extension hip-hop, scene. We've got 2 artists going at it in grime, but most grime fans are actually hip-hop fans these days, so it's being judged by hip-hop standards for the majority. And that trend is only going to grow and continue the larger and more international any uk scene grows. And now proper grime will just be some niche for old cunts like me and musical anoraks. And what is known as grime by many and by general consensus will be to others (or some very passionate fans) what brostep is to dubstep. I.e. it's fairly anal in the eyes of the layman to separate the 2, but if you really are passionate about a specific genre, there are key differences that make one enjoyable more than the other.
Stormzy is making tunes for listeners, for your car, for a concert, for the hip-hop connoisseurs. Yeah he's putting out stuff on grime beats sometimes, and with a grime flow. But there's an emphasis on content and lyricism and polish and albums and videos and just general technicality and professionalism and image that's to be digested critically and pontificated.
Wiley, and traditional grime, is putting out stuff that does some of that, but is really about fucking up the dance and just pure gas.
That's the difference really. And that's the new grime.
Having said that, if it is hip-hop standards, then stormzy's are just not true.