The Rapper = niggas that can make good songs, can create a dope vibe but ain't really saying shit of substance or moves the needle in the art of actual rapping, skillwise. Repetitive but enjoyable content. Sometimes production dependent. Rick Ross, Game, Freddie Gibbs, Spiita, etc.
The Lyricist = skilled niggas that's rapping for sport. Rhyming to out rhyme the last rhyme. Rappity rap. Complex rap schemes and punchlines but similar to the Rapper, ain't really saying shit neither. But unlike the Rapper, can't create musical content or make good songs consistently. Repetitive, headphone music. Crooked I, Eminem, Benny The Butcher, etc.
The MC = The perfect balance of the Rapper and the Lyricist. Can create a radio record, a street record, a deep introspective record, etc. Can perform complex rhymes and flows with meaningful content without sounding boring or repetitive. Displays creativity in storytelling and song creation. The pros of the Rapper and the Lyricist but none of the cons. Nas, Jay, Big, Scarface, DMX, Pac, Kendrick, Drake, KRIT, etc.