The two cards are farily equal in performance. 970 often has an advantage at 1080 (not always, a lot of new games seem to like GCN), but this tends to decrease as resolution goes up, and if you ever intend to use dual cards the 290s are almost undeniably better. Configuration-wise (Shaders, ROPs, buswidth), a 290 is simply 2x7870s in one chip. That's an acceptable baseline to upgrade, imo. Like going Crossfire without any of the negatives.
For US card and electricity prices, it is likely that the lower power consumption of the 970 will never make up for the price discrepency unless you keep the card for many years or use it very heavily for a few. I'm not sure about your country though. The noise can also be negated with a proper cooler (Sapphire Tri X). The heat will always be there, however, so whether in your case or in your room, 290 will always make more heat than 970 so that is a real, hard disadvantage.
If the two cards are priced the same, I'd take a 970 over any 290... unless I want to go multicard in which AMD is simply better. What is the actual price premium though? Depends how much you hate heat and like Nvidia Streaming, if the 970 is worth a large price premium for single card use.