They are in two different categories. The PM3 was designed to be a portable closed back headphone. It's still my favorite portable can to date. The bass is full, the midrange is lush with plenty of body, and the treble is just enough. I prefer a little bit more sparkle up top but being tuned this way lets you turn up the music without any hint of sibilance. The HD650 are open back reference headphones that are meant to be used at home. They are very warm sounding to my ears with a gorgeous midrange. They are rolled off at both ends of the spectrum t but scale well with better sources. Depending on what sound preference you're seeking you can own both and use them for their intended purposes.