If you can, wait until all the dx12 titles start to coming out this fall and also by then all the release date nvidia vs amd drama will have cooled down and we will be able to take a more sober look at the situation. If you are in the market for a high end card, waiting until the big pascal (nvidia) and vega (amd) might be a good idea, because nvidia has no competition in the 1080 range thus far, so they are pricing their upper tier cards ridiculously. Vega might, or might not change that situation (just look at how they dropped the price on 1060 because of the rx 480).
As for amd doing better in dx12 and vulcan, well amd cards are most often beefier (spec wise) than the nvidia counterparts, but on dx11 that extra horsepower was laying dormant, while nvidia pulled out every bit of power they could from maxwell and pascall. DX12 and Vulcan enable the developers to use those extra features of amd (asynchronous compute) much more efficiently, the same way they are doing for the ps4 and xbox1 (both of which have an amd apu inside them), so provided the game is well optimised, you see those enourmous gains, like in doom, for amd, because on top of not being able to use features like asynchronous compute efficiently in dx11, they also had a very large API overhead (the video that i posted above talks about that). Now what remains to be seen, is if developers of dx12 games are good enough to optimize those games to a level that would make amd cards much more efficient. Nvidia cards are still very good even in dx12, but they don't have much room to grow, while amd ones do, but we have to see how things play out once the dx12, vulcan games start comin out (plus, we haven't seen how well their (both amd and nvidia) aftermarket cards lock horns.
