They're identical, and I've directly compared them. I'd get the 271 since you'll save a chunk of cash and get the detachable cord, but I do like the 272 color scheme better. Only reason I got the 272 instead of the 271 was that I found them for sub $150 new.
one has velor type earpads the other has leather type earpads, as mentioned k271 mkii has detachable cable but also has some sort of annoying (or not) switch that turns them off when removed. K240 sounds similar but there are differences no?
the k271 is basically a closed version of the k240MKII and the 240 MKII is the same as the k240 studios. the MKII just comes in AKG's known ''silver'' color to look like their vintage models and comes with extra cable and extra velour ear pads.
i would go for the k240/MKII instead cause it's semi open and will give an impressive of a wider soundstage.