UNIGINE introduced the Superposition Benchmark in April 2017 and it contains a benchmark based on the UNIGINE 2 Engine that is pretty tough on modern graphics cards.
We ran the SuperPosition Benchmark performance test with the 1080P High preset.
The AMD Radeon Vega 56 scored 8,149 versus the 9,135 on the Gigabyte GeForce GTX 1070 . Here the GeForce GTX 1070 is 12% faster than the AMD Radeon RX VEGA 56.
Here are the FPS results from the benchmark that show the Vega 56 dips down to 50 FPS while the GeForce GTX 1070 drops to 54 FPS. Not horrible spikes and if you are playing on a FreeSync or G-Sync gaming monitor neither of these drops should be noticeable.