I'd go for whatever's cheaper, both cards have similar performance. The way I see it, the advantages of AMD are: 4GB VRAM and 512-bit bus width, Mantle API. While the advantages of Nvidia are: Shadowplay and, supposedly, better driver support.
The 4GB VRAM on AMD might not matter now, but in the future, who knows? Battlefield 4 is sometimes using 2100+ MB VRAM on my R9 290, 780 has 3GB VRAM. It's good to have 4GB, especially if you intend to keep this GPU a while longer, like myself.
Mantle API, only a small FPS increase for me, because I have an Intel i5 CPU, this is an advantage with lower-end AMD/Intel CPUs. Then again, this might come in handy in the future, when my i5 is going to get older, Mantle is going to squeeze more FPS from a game, as it removes CPU Bottleneck.
Shadowplay is good if you want to record you gameplay, although you can have something simillar with AMD, as it has an encoding chip like Nvidia's NVCE. With MSI Afterburner, you can use the AMD VCE or, with a Intel CPU, you can use Intel QuickSync, which, considering Afterburner's benchmark, is faster at encoding than NVCE, AMD VCE beign the slowest, for now.
For the driver support, yes, Nvidia has more features within Nvidia Control Panel, like custom resolution etc, but that's about it, I've never had any issues with AMD drivers, and I've been only using the betas.