Crossfire wins in any CFX supported game, it's more powerful than single 980. There are many other factors like TDP, heat, but solely on performance basis, CFX 290X is BEASTLY stronger than single 970.
Well yeah thats basic deduction. I was hoping for benchmarks or the like. A friend of mine is trying to find a 970 but can't due to stock issues. I told her to just get a an R9 290 since her motherboard supports crossfire but not SLI.
I used to have a motherboard with PCI Express 4X and I had crossfired R9 280X with no problem. When I upgraded my motherboard to MSI Z87 G45, it's still the same, no performance difference.