Please note that our "under load" tests aren't conducted in an absolute peak scenario. Instead, we have the cards running a real game, Crysis 3, in order to show us power draw with a more typical workload.
Although the Radeon R7 260X and GeForce GTX 750 offer comparable performance, our test system draws 40 fewer watts at the wall socket in Crysis 3 with a GTX 750 installed. The GTX 750 Ti is similarly efficient, drawing only four to eight watts more than the GTX 750. Maxwell's power efficiency improvements are no joke.
Noise levels and GPU temperatures
I suppose I could have added an extra digit to the acoustic results, so you could see the fine-grained differences between the cards. Truth is, though, that nearly all of them are alarmingly close to the ~32 dBA noise floor for our test system (whose only other source of noise is a big, quiet Thermaltake CPU cooler) and for Damage Labs itself. I don't want overstate the precision of our measurements.
These are, of course, very good results. You won't perceive much difference between the noises produced by most of these cards in normal operation, with the obvious execption of the R7 260X. It's a little unsettling that the Maxwell-based cards aren't any louder when running a game than they are at idle. Even the rinky-dink reference cooler keeps the GM107 at a reasonable temperature without making any more noise.