Like what RPGWiZaRD said, the 2 sound very different.
The XB700 is more rumbly, has softer sounding bass, has greater bass quantity in both mid-bass and sub-bass, has longer decay in its bass presentation, and has better treble extension than the PRO700MK2.
The PRO700MK2 has faster and more punchy bass. Bass quantity is less than on the XB700, but they fare very well with amping. The PRO700MK2 is also a darker headphone than then XB700, and will require some attenuation of the high-end to get some treble sparkle to show up.
You really need to test both out, because you might prefer one over the other. Bear in mind though, if you want lots of bass, the PRO700MK2 might disappoint when auditioned stock (out of the box). They will shine when paired with a good bass boost amp (e.g. E11) and with EQ-ing.