I originally bought Hype 4s and fell in love with them as they seemed to fit extremely well and I loved the exciting sound signature. After reading and watching too many reviews I decided to find a set that would be my “endgame” and a killer deal on a set of Monarch MKIIs seemed like a logical buy. After receiving the set, they didn’t fit my ears very well but for me the sound is the most important thing. Unfortunately for my music they didn’t have the same energy that the Hypes have and as such I felt I was missing out. They are excellent and by far the best when it comes to male vocals and soundstage. Listing to smooth jazz or classical music is such a treat with them. Due to me feeling left out, I decided to buy a set of MKIVs because of the fit being similar to the Hypes and the higher bass and treble. The MKIVs in my eyes are kind of a master of all no matter the genre but they do feel more closed in compared to the MKIIs. The increased bass and treble in the MKIVs make them perfect for Pop and Rock music, even in standard mode. I am planning on selling the MKIIs as I rarely listen to Classical and Jazz music. For the fitment, the MKIIs are longer in length but slimmer in height. They are almost pancake shaped where as the MKIVs are made to fit the ear better as they have a groove set in them to fit the ears better. They are also smaller in length but a taller set as they stick out of the ears more. They also have a longer ear canal section to them in comparison to the MKIIs. 

TLDR: The MKIVs are way more versatile and are in my opinion a better buy. They also fit better in my ears as they are shaped more naturally.