Performance wise both cards are fairly close at stock. So with that being the case, we're looking at a situation where both cards are similar in price. Let's see.
First, if you get the 290 do not get reference. IMO, the reference design leaves a lot to be desired. If you want a 290 get an aftermarket variety, they are the only reasonable choice for AMD 290 cards. And i'm sure some here will argue in favor of the reference 290 till they're blue in the face, but the card is not quiet. Maybe you don't care about quiet. I don't know. But keep that in mind. The aftermarket 290 cards fix the reference blower problems and perform quite well. Very well, actually.
With nvidia you can really get either or, although the aftermarket cards will be significantly faster with GPU boost 2.0 + overclocking. GK110 overclocks better than Hawaii from what i've seen. So if you go nvidia route I would suggest aftermarket if you want overclocking, as these cards are scaling 15-20% past stock reference with GPU Boost 2.0.
My opinion is also with both being the same price, get the 780. My opinion is NV offers better and more polished software as has been mentioned by a few others in this thread, and I do like their added features such as adaptive vsync, driver AO, downsampling, monitor overclocking, etc. This is just my opinion having used both AMD and NV extensively over the years. I'm sure some will get offended, disagree, whatever, but this is an opinion thread and this is mine. Generally speaking I haven't had a situation with NV where I had to wait months/years for a fix to a problem. That has occurred on the AMD side in recent times with eyefinity, and is quite frustrating if you're on the receiving end.
I think that nvidia clinches it by a mile in terms of software/drivers, but don't take my word for it. Search around, do research, and look up what each card offers you in terms of features and software. You may not care about nvidia features or may be interested in Mantle...if you aren't interested in those NV features / software, weigh your purchase decision accordingly. Like I said, at stock both cards are close in performance. You will probably be happy with EITHER card in terms of framerate. They are both disgustingly fast for 1080p. So you'll need to weigh your purchase on software, features, and all that sort of thing. I have my opinion on software and features, yours may differ. Do some research, hit up google, and go from there.