Yea the real question is what you're willing to spend for a small boost. As Craig pointed out, the 290X is the better of the cards... but TBH, I have the R9 270 and run all my games on max settings (mind you, I don't have any games newer than 11/2013). An interesting quote though;
"Playing video games for the graphics is like watching porn for the story."
How good the game looks does not translate to gameplay satisfaction or 'replay-ability.' If the game sucks, the best graphics in the world will only capture your attention for about 5 minutes.
Again though, it's entirely your decision. I would personally save the money and get the R9 290, but it's your money, and if you can afford to spend the extra cash on the 290X, by all means go for it.