Well Eminem can slaughter anyone so that's a given, i'm not much of a fan of his music but I give credit where it's due.
For sure, the other artists are dancehall artists so it's on the Jamaican side of things but it's pretty interesting once you get into it. The UK rap/grime scene has always been influenced by the Jamaican clash culture so that's how i've gotten into it.
I'm not huge into this genre much, but I am def more into the hyphy scene (Mac Dre, E40 etc) than the rest of the subgenres.
I know maybe people think its too mainstream, but my favorite pac song is changes. Especially with today's atmosphere, even more applicable than when he dropped it.
Also, damn it feels good to be a gangsta, one of my favs.
I don't really know much about different diss tracks. Although more in the rock genre, I would say Foo Fighter's "I'll Stick Around" is pretty good. Also, Sweet home alabama was an early mild one.