Power, Heat, And Efficiency
AMD's latest Catalyst drivers override AMD's firmware settings, resulting in the Quiet and Uber modes performing pretty much the same (at least according to the results of my maddeningly-long time in the lab with these cards). The only difference I found was that the air-cooled card reached a lower idle state in Quiet mode, and I'm using that more conservative idle state in these power numbers.
The system with our air-cooled Radeon R9 290 only idles down to 102 W with the Uber firmware selected. Overclocked, the air-cooled card could have dropped to 105 W if we were using the Quiet BIOS and our more aggressive clock rate settings. Conversely, VisionTek's CryoVenom R9 290 doesn't exhibit the same behavioral difference.
The overclocked air-cooled card's higher idle temperature can be partly attributed to the fact that its power consumption doesn't drop as low with Uber mode engaged. I checked, and at the same clock rates, Quiet mode would have allowed it to drop to 22 °C over-ambient.
Overclocked, the retail card's lower temperature comes from a higher fan speed that adversely affects noise.
Less thermal throttling allows VisionTek's CryoVenom R9 290 to gain 2% performance over the air-cooled board running at the exact same frequencies. It also enjoys 6%-higher overclocked performance.
Using the stock Radeon R9 290 as a baseline, we find that the CryoVenom can improve efficiency by up to 19% under the effects of overclocking. It's even 11% more efficient than the stock card, using the same BIOS, at stock clock rates. Lower temperatures do wonders for efficiency.