Drivers are different. 15.10 vs 16.7.2
That 290X (reference VTX3D with a new Board) needs to clock 100MHz more over the older reference cards to equalize performance. Not sure why. Board seems pre-Grenada (with printed 8GB/4GB markers).
480 is good for starters. Not worth it really for Hawaii and Grenada adopters. Unless you really mind power consumption.
The Nitro runs pretty cool! But I won't stick woth this card. It clocks very low for my liking.