I can share my experience with these 2 headphones but ultimately I would suggest you give each of them a listen before purchasing, if that's possible of course.
First off, build. The LCD-X feels very solid and is very well built, but it's massive. It's weight will have a negative impact on long term comfort. I've had issues with my ears touching the fazor elements too. The Edition X V2 on the other hand feels flimsy and fragile, build quality is frankly not the greatest. However it is very very comfortable due to the suspension headband and lighter weight.
Sound wise I found them both very enjoyable. I didn't have any issues with the treble region being too recessed but I'd say the Edition X V2 is the more balanced of the two. I found the LCD-X to be a bit too bass heavy, even feeling muddy at times. The Hifiman had a more airy sound, felt wider than the LCD-X, but still had good bass. I was impressed with the detail retreival on both these cans.
Hope this helps