The sig of the TMA-1s is definitely a love, hate or EQ affair. If you don't mind EQing, they respond remarkably well. If you don't like EQing, you'll either hate them or you'll love them, or you'll only like them for their strongest genres like electronica. They are a warmer version of the HD25s. If you have the right set-up, the HD25s have more punchy bass, but without the right set-up, I'd say they were about equal (though from my Cowon J3, the HD25s were still better, but I needed to up the volume a fair amount more). The great thing about the TMA-1s is how easy they are to drive. For people like me who wants their portable rigs, portable, having a 32ohm impedance helps vs the 70ohm HD25. That said, for most music, unEQed, I prefer the sound of the HD25s, but EQing closes that gap pretty decently (but you need a full EQ, the iPod EQ is simply not enough. You need EQu or Cowon EQ or Rockbox Sansa EQ imo). The TMA-1s never have the same highs, but they become much better while retaining their non-fatiguing sound.
As for comfort and clamping force, the TMA-1s are interesting to say the least. They have high initial clamping force, but because of their build materials they decrease over a period of time. The clamping force remains fair enough for train rides, but isn't consistent like the HD25s. And that is where their comfort comes from. The fact that they use rubber materials to build them instead of hard plastic gives them durability and comfort, but it takes away from the clamping force. The HD25s on the other hand uses a high quality hard plastic that is durable and retains its clamping force. So less comfort for more isolation. If you wear glasses, the HD25s may not be the best fit. With my regular glasses I never have a problem with the TMAs, but start feeling discomfort with the HD25s. With my sunglasses, they are both pretty bad, but the TMAs improve (ie, if it was cloudy and I was already wearing my TMAs and then had to put on my sunglasses later), but not enough to say they are completely comfortable.
That said, I cannot say that either the TMA-1 or the HD25-1 II is significantly better than the other. They are both really good headphones that are both damn near indestructible. I've only briefly demoed the M80s and my initial impressions were the same... Really, if I had the money to waste, I'd get either the M80 or HD25 to compliment my TMAs, but I think instead wait until I have enough to buy a proper portable upgrade.