Between the Element and HPA-2C both are excellent, the HPA-2C has the slightly warmer smoother sound, the Element is very neutral and looks amazing, along with being very small and powerful.
Both excellent choices.
I personally don't use balanced, don't have the equipment, and there are misconceptions about balanced. My point being they could have used 4 pin instead of 3 pin just for those who want to use them balanced, wouldn't have changed the design or anything.
Same as the DT 1770, it means you cannot run them balanced as it is only 3 pin, I think they should have used 4 pin personally. But a lot of people mod headphones for dual entry for balanced either way, but it would have been easier to have 4 pin in the first place. I suppose you could just swap the 3 pin out for a 4 pin as they would be the same size.
Just to let you know the New Beyerdynamic DT 1990 Pro will be at CanJam London, the first time it will be shown anywhere, as it's official release is only at the IFA show in September,