The T70 is definitely far better than the DT990! The resolution of the T70 is in a much better league. The only thing I can think of where the DT990 is "better" is in bass impact if that is what you are looking for. The T70 beats the DT990 in every other way if you ask me and I do prefer the tight and punchy bass of the T70 by far.
I have to agree, for me the T70 could use some more bass impact though.
As I'm not using my T70 at all, I'm thinking of selling it actually