I've got/ used both - had a corsair hg10 n780 on my 780Ti and currently have a kraken g10 on my 980Ti in my new gaming rig. Both times with a corsair h55 unit. Honest summary from experience....
The corsair hg10
Fitting
theoretically easier to fit and set up as it has everything you need in the box. However, I actually found it very confusing and difficult to setup, the instructions were terrible and I ended up winging it and not using the bracket it was telling me to use etc etc. The 980 version has also been recalled recently due to mounting issues and the fact it can bend cards too much.
Performance
Very good. Dramatically lowered temps on my 780ti. The whole unit also acts a heat sink and cools all the ram and vrm chips
Looks
Personally, I think it just looks clunky and a bit fuddy duddy. Not a fan to be honest.
Kraken g10
Fitting
Depends on your cards makeup, whether you have a backplate, mid plate or whatever but in a way I actually found it easier to fit the kraken. This may have been because it wasn't my first go at this type of thing, like it was with the corsair one. It's just a lot more straightforward in many ways.
The thing with the kraken is, for me at least I was going with a whole more 'modding' mindset before I started so I was prepared for hassle and to put some research and work in. I'd read the criticisms about it not cooling the vrm chips enough, so I did some full research and bought lots of bits including small heat sinks, Akasa thermal tape for the heat sinks, a noctua 92mm fan and a geilid adapter to attach the fan so I can control it via GPU temp via afterburner.
As such it was a bit of a project and took me a fair few hours to prepare and do. It even involved me having to hacksaw some of the heat sinks, and I had to clean all the glue off with solution before applying the new thermal tape etc etc.
A lot of hassle many may think, but You know what though, I enjoyed it, and I'm very pleased with how it went and the results!
Performance
Very good. dramatically lowered the temps of my 980Ti. I've got a vardar fan on my radiator heat sink now and have spent ages finding a balance between rpm speed, quietness and performance.
The 92mm noctua fan is fantastic, so quiet, but I never run it past about 75% speed. The heat sinks feel rock solid and hopefully are doing the job
Unfortunately I have no way of monitoring the vrm temps on the 980ti, or the 780ti so I have no stats. There is no software that reads it, and from the scant info out there I don't either card has vrm temp sensors built in.
Looks
I actually prefer the look of the kraken to the corsair hg10 by a long way. My card has a backplate, and the black kraken bracket compliments it very well. It looks
**** hot in my new case and system, a lian li pc08 case which is all smoked tempered glass and controllable led lit.
I'd say that looks pretty good
Summary
I'll be honest, if the corsair n980 bracket hadn't been recalled, I would have got that for my 980ti, just because it would have been a bit easier all round for the reasons above.
But, having said that, with the results I've got with the kraken, how it looks in my case, and the fact that I actually enjoyed doing it all, I'm tipping it to the kraken g10.
Also, whoever you go for, in summary I think AIO coolers for GPUs are the way forward. Never going back to air coolers now.