I tend to avoid unnecessary comparisons. I don't think they are comparable in any way. The Phoenix isn't as open as the HD 598, while the HD 598 doesn't have anywhere near the bass response of the Phoenix.I saw you mentioned the Sennheiser 598, can you compare the sound of both?
The HD 598 will remain my baby. It's my holy grail when it comes to "old-shool" quality. The quality of the plastic on the HD 598 truly seems to be German-grade (Germans are known for having everything high-quality.... at least they were, I don't know how it is now). The cable on the HD 598 remains the best cable on a headphone that I have seen, the new cables on headphones are crap. The HD 598's cable is close to the quality of MacBook's (mine is the early-2015 version) charger cable - indestructible.
But quite honestly, they are two very different headphones, especially considering that the Phoenix's driver sits very close to the ear. The HD 598 is just a classic, I can wear it for days. To say they are very comfortable would not be enough, because they just disappear on your head. Also the pairing of HD 598 to the Earmen TR-Amp is just unforgettable, the chemistry between those two is *mind blowing