As you may notice, the HIS card runs a lot more cooler than the gigabyte one under load, leaving much more room for overclocking. His cards are pretty good overclockers aswell. This particular HIS card has lower stock clocks than the gigabyte one, so it does overclock slightly worse, but the difference is marginal.
The HIS card is also smaller, which makes it easier to fit in into some cases. It is also quieter than the Gigabyte card under load, (38 DB vs 44 DB). The HIS card has a little bit worse stats than the gigabyte one hardware wise, but they only affect so little, that the difference is marginal, perhaps 1 fps if even that.
Overall, I would personally pick the HIS card based on the above reasons.