I currently have the Ultimate Ears Triple.fi 10, Super.fi 4, Sleek Audio SA1, SA6, Monster Turbine normal, and Beats Tours.
I listen to a variety of music, but I tend to favor rock, metal, acoustic guitar, orchestra, and any venn diagram overlap of the previous four.
I also play in an orchestra, so I'd like to think my ears are particularly trained, but who knows? I'm sure there are plenty of audiophiles out there who can listen to music just as well as I can.
When listening to music, especially orchestral, I tend to listen to how the timbre of the instruments are conveyed, as it helps me practice my own instrument. This also lets me know how the IEMs perform with what genre of music. For example, I was trying to listen to Beethoven's 4th on the Beats Tour, but couldn't get very far as the bass was much too over emphasized, the same (mostly) goes for the Turbines. The opening was superb, but once the full body of the orchestra came in, it became too much.
I found that the SA6 and Triple.fi 10's performed best on classical pieces.
Surprisingly enough, I felt that the SA1's performed really well on acoustic guitar pieces. Maybe the rosewood body added warmth to the sound or something, I don't really know, they just sounded amazing.
Anyway, hopefully the above information helps you in your selection process!