As a person who prefers Nvidia (most of the time) yet believes the roll of AMD is important I would say that the 290 is the more powerful card overall.
Currently the Premo (yet not stupidly priced) GTX 770 is the EVGA dual ACX Superclocked 2GB which runs about the same price as a low-end 290. The benefits of the 770 in this case would be the 3 Year Warranty that isn't voided if you overclock, swap out the cooler, or do some light tinkering (EVGA only) and it's amazing reliability on a well tested platform (GK104, formerly the GTX 680 heavily modified).
Look up your favourite games and compare benchmarks from the two on the 770 and 290, just keep in mind from most benchmarks I've seen the 770 is infinitely better at getting much cleaner frame time results which gives you a very noticeable smooth experience. In contrast to this there are a lot of games that the 290 and 290x have notorious 30 FPS or bad frame times in. Like I said research on what games you plan to be playing and make your purchase based off that.
While the 290 is a fine card DO NOT purchase it with it's stock cooler. It is quite possibly the worst stock cooler shipped with a high-end card that AMD have ever put out. Look up what the card sounds like at 50%, and 100% fan speeds.
Sources: 2 builds for clients using 770 and hand-overclocking it, 1 build for a client using stock cooler 290 (we bought the 290 right when it came out, for her, she came back a week later and said she didn't care how much it would cost she needed an aftermarket cooler ASAP).
It literally sounds like a hairdryer at full blast inside of your computer, I'm not over exaggerating.