I've heard the Sennheiser Momentum 2.0 and HD650. Similar mids, that's it. The M2 has more and extended bass and low mids, and brighter highs. The HD650 is a bit more spacious and refined sounding overall. I received and tried the new HD 4.30i and it's going back. Lightweight, good looking, well built. It barely opened far enough to reach my ears on my very large and long head.
Pads are soft, but they'll show a shine really fast from skin oil. Even cleaning it off it retains some shine. Material feels very artificial vs. other kinds of pleather. Pad openings similar to M2, which while bigger than M1, were still too small. My ears are above average sized, and the pad sits on the very top and bottom parts, not around it. Soft pads, but still after a while that gets bothersome.
Soundstage was average to small. Highs and mids are great. Seem a bit warmer than Momentum, but clearer than HD650. Low mids are good. A little more mid bass than I'd like, but subs are great and extended. Sound was a lot like the Samson RTE X noise cancelling portables. The Samson don't fold like these, but go flat to fit in their excellent small hard case. These have no hard case.
The earpads on those Samson are not quite deep enough (as these were) but were a bit larger for openings to just barely fit my ear. Sound quality is similar in NR mode to these, with the bass being a bit tighter, and the highs a bit brighter on the Samson. So for $99 (the same price) I much prefer the Samson RTE X fit, comfort, portability, accessories. Sound is similar, NR is a bonus.
That said, the Sennheiser 4.30i really isolate well. For passive headphones, their spectral balance (besides a little too much mid bass) is exceptional. It's a nice new direction at a low price for them, they've just got to test these better. So many portables suffer from small ear pads. The Oppo PM-3 shows that you can be portable / small / folding, with large comfortable ear pad openings.