The R7 260X's higher clock speeds have a drawback: a 16W hike in load power consumption compared to our 7790. Idle power draw is similar across both cards, however.
Noise levels and GPU temperatures
The R7 260X runs measurably hotter and subjectively louder than the 7790, but I wouldn't worry too much about that. Our sample of the R7 has a stock AMD cooler. Stock coolers rarely, if ever, find their way onto retail cards in this price range. Our 7790 has a nice Asus dual-fan cooler, and I wouldn't be surprised if retail R7 260X models shipped with similar cooling solutions.