Okay, so I spent some more time with them, and I don't think they'll be replacing my Momentum 1 as my commuter headphones.
COMFORT
Sony wins hands down. The Momentum does pinch my ears and after an hour or so I do want to take them off to give my earlobes a break.
ISOLATION
This I guess is the biggest deal breaker. The M1 has significantly better isolation. I was testing in a busy store environment, which is precisely the kind of place I will be using these headphones in. In fact, on the train, I will need even more isolation. Even the man next to me speaking with a deep voice was very disturbing to me with the Sony, so engine noise will be a problem.
SOUND
It's a moderate, warm V-shape from what I could discern. It's more balanced than the M1, no doubt. Also a much more balanced headphone than the MDR-1A. It doesn't have such a strong signature as the M1, which has a dark, rounded-off kind of sound. However, there were a few things that made me still prefer the M1. The first is the cohesion of the bass in relation to the lower midrange. Say all the mean things you want about the M1 treble, I find the transition from bass to midrange quite natural on the Sennheiser. Because these headphones *need* good classical music rendition (classical music is my profession), I took 2 test tracks I like to use to measure several metrics. Wagner's Tristan und Isolde Overture, Karajan version, I dont' know what year, I listen from about 6:30 for about 40 seconds. This part has long, deep double bass lines along with upper strings soaring above. What troubled me was that the bass seemed too disconnected from the whole - usually a sign of a recessed lower midrange. Indeed, the first violins and basses come through clearly, but I have to strain a bit to hear the second violins and violas clearly. Next track, Carlos Kleiber conducting the Fledermaus Overture, Bavarian State Orchestra. I listen from the start for about 40 seconds here as well. It's usually a test for stridency in the upper strings. The Sony passed that test, the first violins sound great, more natural and clear than on the M1. However, the opening 3 notes are underpinned by timpani strikes - the M1 renders the timpani clearly here, with decent articulation and impact. On the Sony, unfortunately I wouldn't even really be able to tell that timpani were even in the score - the timpani hits came across very undefined and flabby. At the 15 second mark, the violas come in with the "rhythm section", and here the lower midrange recession is again apparent on the Sony. Same story at around 29 seconds, when the second violins answer the first violin melody with a staccato arpeggio - just lacked some bite here. Even the dark M1 brings this out better. Moving on to some jazz, I found vocals to have more pleasant fullness and presence on the M1, although the flaws I heard in the classical tracks were much less of an issue. Now we're getting into conjecture territory, but I found generally in the midrange that there was a bit of artificial sounding smoothing happening, like when somebody over-Photoshops a beauty portrait and removes all the pores. I am just gonna go out on a limb and say that CSD measurements are going to show some ringing at say 5K, or thereabouts. It's one of those predictions that make you look like a genius when you're right, so here I am making it. Oh, soundstage is wider on the Sony, so one point for the Sony there.
TL;DR:
Lack of isolation is a bummer, I can't use these on the train with so little of it. The sound, while on the whole more "balanced" than the M1, it's not an outright win in any way. If you don't need much isolation, and want a smooth, good all rounder, I think these would be a decent choice indeed. I enjoyed them more than the AKG K545, and they're for sure better than the 1A. Probably sonically more appropriate for most tastes than the Momentum, but I just have a rather strong dislike for lack of cohesion of bass and lower midrange, and would even sacrifice treble for it. So in terms of an M1 replacement... still searching.
