AKG K271 mkII/K272 HD:
Neither are going to be terribly portable. The main differences are the color, the K271 mkII coming with both pads (velour and pleather), and detachable cables, coming with two of them. However, neither cable is short, and the shorter one is more "microphonic." I can't say fir sure, but I would guess the integrated cable of the HD model is probably much less "microphonic."
I'm not sure how well isolation will be for your intended use. The isolation is good, but not great, from the lower minds/upper bass on down (I'll guess <500Hz), which will account for a great deal of the noise in buses and trains. Above that it's similar to the hard silicone Shure tips.
Comfort, OTOH, is phenomenal (with velour pads, of course).
Yet, while they boast of efficiency, they really just mean sensitivity. If you have a nice portable amp you use already, you should be set; but, they benefit greatly from an amp when it comes to long-term listening. The upper-mids have a sibilance to them, and the mid-bass has a dip, which combined with phase distortion from little cap-coupled outputs can make it sound like there are two instruments making every low drum hit.
I'll leave others to those Senns.