I think mike does a good job explaining the differences.
yes, but thats just so they conform to your ears without feeling like you're wearing a clamp on your brain.
on a side note, I am really digging them as a portable. Dont get me wrong, the TMA-1's are phenomenal, but the HD25's have such an engaging/electric sound to them that the TMA's cant do without a good EQ'ing. I also like how the finish isnt as delicate as the TMA's; which means I dont have to worry about exclusively placing them down on padded surfaces.