The temperatures of both GPUs were within safe limits at load, and they idled in the same range. The problem with comparing GPU temperatures comes down to the performance of the cooler, which is generally comprised of a heatsink and fan. An open variable comes from fans. Fans in the coolers of video cards are usually setup with variable speeds. When the temperatures are higher, fan speeds are higher ... and vice versa. I'll touch on that shortly when discussing noise. Just leave the GPU temperature section knowing that both video cards were installed with capable coolers.
Power usage between the 6870 and GTX 560 are close. At idle, the GTX 560 uses 9W less power, but at full load the 6870 uses 7W less. As most systems spend more time in an idle state (or close to), the GTX 560 is a little bit greener than the 6870.
Ending this section with noise, I don't yet have a standardized practice in place studying the noise output of hardware. But after using both video cards while gaming, I do have some subjective observations. When idle, the coolers on each of the two video cards are essentially quiet. With the load of an intensive game, things change on the noise front and the fans speed up.
With XFX's Radeon 6870, it seems like XFX set the variable fan to be quite aggressive. This results in lower temperatures, but at the expense of a noticeable whine. As discussed earlier, the temperature of the 6870 GPU was held to safe levels with its cooler. XFX could have been less aggressive on the cooling front to reduce noise levels.
Zotac's GTX 560 on the other hand was noticeably quieter. I could notice when the fan speeds increased to match the increase in load and temperature, but it wasn't as drastic as XFX's cooler on the 6870. With a heavy load on the GTX 560 GPU, I would describe the noise generated by Zotac's cooler to be a noticeable hum. It's noticeable when you try to focus on the sound, but it blends more in into the background.
In performance testing, I found that the XFX Radeon HD 6870 (1GB) and the Zotac GeForce GTX 560 (1GB) were both capable in performing with very high (mostly maxed) out settings with the games in our test suite at 1920x1080 resolution. As per Steam's hardware survey, this resolution is the most popularly used by gamers. It should be no surprise since most 22-24" monitors and modern flat screen TV's of all sizes use this resolution.
While I didn't test any other GPUs (as this is my first graphics article here), we know that the Radeon HD 6870 and GeForce GTX 560 are faster than the modern Radeon HD 7770 through the testing done by my colleagues other hardware review websites. The main tangible benefit of the 7770 compared to the GPU tested here today is improved power savings. But for gamers, this benefit is second to gaming performance. And this is where the Radeon HD 6870 and Geforce GTX 560 win.
The only problem (and it's a BIG one) is production has ended for the Radeon HD 6870, and I'm presuming will end shortly after the GTX 560's successor is announced. Watching the past few weeks, prices of video cards based on either of these GPUs have been dropping slowly. Availability is finite, so if you want a good video card for a steal of a price, now is a great time to buy.
At this point near the end of their lives, XFX's Radeon HD 6870 and Zotac's GeForce GTX 560 both earned our Bang for the Buck award! This value based recommendation extends to other video cards in the $150 price range (or lower) with the Radeon HD 6870 or GeForce GTX 560 GPUs.