Never had both at the same time. I would say the SE on the phoenix is better, but I have no way of verifying this. There is seemingly more energy and impact w/ phoenix, but again its not like I matched volumes and etc. The concerto seemed a little clearer, but the phoenix kicks really hard and overall has better detail.
I always wanted to turn the volume up on the concerto, whereas with the phoenix I am happy keeping at a given position... but again lol could just be the lower positions are louder relative to the concerto.
Either way you will be a very happy man. Bare in mind you are only using half of the phoenix if you use SE... Going balanced is a snap is your headphones have 4 conductor cables though... if not the concerto surely is the better deal, because the sound is very close and if you don't need xlr there is a lot of wasted options on the phoenix.