i hate to say it because out of all the sehnnheisers i have owned over the years, it was the most dissapointing, but in this company it has to be the 280's.
I have only tried Senn 200/215/280. Of these, I liked the HD280 best, bought them, and have been using them for about a year. It blocks external noise pretty well, but louder surroundings require some volume to effectively block the noise. My only complaint is that I find the pressure on my head uncomfortable after a couple hours.