The SM2 is clearer in the mid section which is probably its most forward section. But, it is not easy to drive. If you have a nice amp, you will hear very good instrument separation, a deep bass and for a dry earphone, pretty emotional mids. Without an amp, the IE8 can outclass it in resolution in many ways. I don't really like the IE8, but I recognise that it has a lot to offer.
Personally, I prefer the SM2. It has a stronger cable which won't pull apart at the stress relief or suffer pin bends. It also seals and can be used outdoors better because the driver won't crinkle from sudden air intakes.
And, it has no problem with mid bass hump. That said, turning the driver's nob to full, fixes a bit of the IE8 hump, and it can be driven a lot easier compared to the SM2. If you want to hear as much as possible from a dap, the IE8 is a better choice. If you don't mind an amp and prefer isolation, the SM2 is probably the better buy.