As much as I love the sound of the iOs, the built and metarial quality is not up to par. After just one year of light-medium usage, the padding looks like it's a few years old and started to peal. Also, the paint on the cups easily chips away. In comparison, my previous Momentum M2s looked great even after 5 years of use, with no cracks in the pads leather or paint chips, although I took more care of the Dalis. Also the Sennheisers cost me half the price of the iO 6s.
Having to replace the ear pads every year is kinda disappointing...