Benchmarks: Battlefield 4, Thief
Here we see that the GTX 980 Ti SLI cards were just 1fps slower than the R9 Fury X Crossfire setup when comparing average frame rates. However, overclocking the R9 Fury X Crossfire cards only gained an extra 2fps while the GTX 980 Ti SLI cards became 13fps faster once overclocked, making them 13% faster than the Fury X cards.
Despite seeing similar performance between the Crossfire and SLI setups when looking at minimum and average frame rates, we see that the Radeon R9 Fury X Crossfire configuration is considerably faster than the GTX 980 Ti SLI setup when comparing 99th percentile performance.
SLI scaling was surprisingly weak in Thief as the GTX 980 Ti SLI cards were just 18% faster than a single GTX 980 Ti. This meant that the R9 Fury X cards were 50% faster and 82% faster than a single Fury X.
The weak scaling performance of the GTX 980 Ti looks even worse when examining the frame time data. Here the GTX 980 Ti SLI cards were no faster than a single GTX 980 Ti, allowing the Fury X Crossfire cards to deliver 107% more performance.