I own both and have been doing a lot of comparison listening. I really liked the t90 when I got it last yr but now since I bought the 650 I can’t go back to it. The t90 is more open and transparent and works very well with pop, rock and jazz but I find it too bright for Classical which is what I listen to most. Both I find comfortable to wear. No issue there. The t90 is better built and more upscale looking. I find both have similar mids and bass however the 650 lower mids are warmer with a more forward perspective. The t90 has the edge in transparency and soundstage but not by a lot. In the end it’s the upper treble difference that does it for me. I just prefer the more laid back string tone the 650 offers. So I am definitely selling the t90. It’s the Special Edition Chrome model. I have it listed on Amazon for $289.