I made some "strange" experiences during my battle.
Most of the people said, that the sound signature of the T1 is darker compared to HD800 but for me it is the other way round. My T1 (SN 64xx) has a cooler sound signature than my HD800 (SN 14xxx). Maybe due to the changed setup for the newer HD800 models. Did someone from you make similar experiences ?
How is the sibilance on the HD800? If the HeadRoom chart is anywhere close to accurate the HD800 would probably be a little more pronounced for most sibilance but for certain voices the higher treble peak on the T1 will stick out a lot as well.