The 8GB Nitro seems much better than the Asus Strix. The quiet mode outperforms the Asus and is quieter than it. The Boost mode manages a tiny bit more performance but adds a lot more noise, as an option for those with a good noise cancelling setup or are willing to tolerate the noise.
Now the caveat is that the Asus Strix targets a lower temperature. So with a custom fan curve set to the same temperature this may not be necessarily true. The Strix also uses less power, but again is a bit slower. Just from what we see here though, I'd favor the Nitro unless you are really concerned about power consumption (get the 1060 then maybe?).
The 8GB Nitro is 10-11% faster than the 4GB Nitro. Significant enough to where the 8GB with boost can beat a 1060, but the 4GB lags behind even with boost.