Wow, you're really willing to wear big headphones for portable use. I wouldn't touch either of them on the road, but I guess if I had to choose I'd go K271S, which wins on SQ and isolation, and on comfort as well if you get the velour earpads. Is it twice as good to justify the price? No, but headphones rarely are from price bracket to price bracket. But really, if I wanted a full-size dynamic for portable use, I'd go for an old-series DT770-- much less bulky, easier to drive, and more durable than the K271. I was surprised when I saw a couple of people using them portably in Berlin: they really didn't look that big or silly. Come to think of it, a DT100 or 150 would also be pretty sweet as big portables. I change my vote: go for the classic Beyers, and let the public quake in fear!