I found it difficult to find an unbiased comparison between these two mid/high end 7.1 headphones so thought I'd contribute to anyone wanting to know the difference. I now have the chance to do a side by side comparison.
First I just want to point out that I own both of these headphones for some time so can say that I am completely unbias.
They are both headphones that won't disappoint. You'll find the Kraken's have a deeper bass where the Cloud 2's have a far better fidelity. Moving from a Kraken to the Cloud 2 you feel you miss the bass. Moving back you realise the bass is perhaps a little over exaggerated, and the clarity in typical voice and hi-end frequencies are just not as clear. As a sound range goes, it's clear the Cloud 2's are better, but that isn't to say that the Kraken's are bad at all. In fact they are excellent, just not as excellent.
The build quality of the Cloud 2's are better too. The materials are more solid and leaks less noise. The braided cord is softer which on the Kraken causes a lot of noise in the phones whenever anything touches or rubs the cord, which is all the time. You can wear either for extended periods, but I'd actually say that Kraken's are better in a warmer environment over extended period of wear.
One thing I like about the Kraken is that microphone can be pushed into the headset whereas the Cloud 2's is detachable. Detaching isn't as convenient so I tend to just leave it there where I can just push the Kraken one out of the way when not in use. The microphone on and off button in the stem itself as well as having a light to show if it is on and off is also a very practical feature. The Cloud 2 has the on/off switch on the USB control so is hard to tell if its been disabled or not without inspection.
I do like the controls on the Cloud 2 USB control "fob" and it gives a nice long cable to work with. You can plug the headphones directly into a standard 3.5mm phono socket including the mixed audio/mic ones you have on phones and laptops though I haven't fully tried this yet to see if the quality is still as good as the USB soundcard.
If I could only choose one, I would personally recommend the Cloud 2's.