I will update my position on the 1000X after a little more time I feel that the quality of the treble on the P7 is also higher with less grain. Again, we aren't talking significant, but nonetheless audible differences.
OK, I 'bit the bullet' and bought a set of MDR-1000X's. I'm a long-time advocate of the P7W's, and I still think they're astounding BT headphones.
So...? In one sentence: The P7W's are true audiophile headphones. The Sony''s are NOT IMO.
The B&W's truly immerse you in the music, and you feel like you're in the concert hall with the orchestra. With the Sony's, you feel like you're sat at the back of the hall, listening to music 'in front' of you. The 1000X's sound no better than the 1ABT's IMO, and I think they share the same drivers. Which isn't too bad a verdict in itself, as the 1ABT's are very good cans.
However, there is a sense of intimacy listening to music on the B&W's, that the Sony's can't touch. And I'm not surprised. The B&W's have set 'the bar' very high indeed.
BUT, the Sony's have absolutely astounding ANC. I commute to work daily on noisy diesel trains, and the Sony's ANC is very, very, very good. They manage to eliminate the background noise that the B&W's can't. The only problems I've had with the ANC is with sudden changes in wind, and carriage pressures caused by fast passing trains etc with the train windows open. When that happens, you get a strange 'pumping', pulsating sensation in the cups, which totally ruins the sound. However, I think that's a pretty tall order for ANY noise-cancelling headphones to cope with. I would imaging if you're sat on a modern inter-city train without the same problems, or a flight, then the Sony's would have no problem at all in eliminating the background. In defence of the B&W's, they do go a lot louder than the Sony's with the same source, so that helps counter the lack of ANC. But once you've heard what the Sony's can do with extraneous noise, you go: WOW!
Other Pros & Cons:
+ Sony - NFC making connection a damn sight easier that the B&W's. The B&W's have to be paired without NFC.
+ Sony - A nice, study carrying case, that can stand the rigours of daily life. I was never a fan of the B&W 'faux leather' envelope, which in real life offers very little protection.
+ Sony - Voice commands which make using it more intuitive, rather than the random chimes of the B&W.
+ Sony - A more 'complete' package, with sturdy buttons/controls, NFC etc, rather than the el-cheapo buttons found on the B&W. I also prefer the design of the Sony's, and the way they fold completely flat.
+ B&W - MUCH louder, with a greater volume level, although the Sony's ANC is so effective it makes high volumes on commutes a little less necessary.
+ B&W - Pairing two devices at the same time is a cinch, and the Sony's can only pair with one device at a time (I think?)
+ B&W - The B&W's switch on a little quicker, and are a little 'snappier' in operation than the Sony's.
+ B&W - Proper leather ear cups, which I find better than the artificial 'pleather' on the Sony's.
So, which one is 'best'? That's an impossible question, as I genuinely think they have different uses. If I was going for a walk, or in a coffee-shop, or a relatively quiet environment, the B&W's get my vote, due to the demonstrably superior sound quality. But on the noisy daily commute? I think the Sony's win hands down.
I think I'll be keeping BOTH, and both are a cracking pair of cans well worth the £300 price tag.