Canon EOS T3i High ISO RAW
We've recently started looking at RAW files converted with dcraw, an excellent freeware raw converter. dcraw usually offers timely support for the latest cameras, but more importantly, it does not apply any noise-reduction, sharpening or other corrections such as geometric distortion correction to the output files. (We found that Adobe Camera Raw still applies some limited noise-reduction when its NR settings are set to zero, and it also applies other corrections depending on the make and model of the camera). There will always be differences between RAW converters, in terms of the sort of de-mosaicing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color RGB pixels), but dcraw seems to use a fairly generic algorithm that delivers good sharpness with relatively few artifacts, and can be counted on to not apply any noise reduction if you don't want it to. (That said, looking at the ISO 6,400 and above examples below, it's clear that dcraw's de-mosaicing approach does have some tendency to produce rectilinear artifacts in response to high noise levels.)
Below are crops from Canon T3i's 14-bit RAW files compared to RAW files from other consumer SLRs, converted with dcraw.
The crops above compare the Canon T3i's RAW noise performance to that of other similarly priced consumer models. All cameras were equipped with our Sigma 70mm f/2.8 EX DG Macro reference lenses, stopped down to f/8 for maximum sharpness. As you can see, the Pentax K-r produced RAW files with the lowest noise, though it also has the largest pixels (lowest resolution), giving it a slight edge in light gathering capability per photosite. The K-r also applies some subtle noise reduction at ISOs above 1,600 that can't be disabled, which leads to cleaner images but also to some blurring. The Nikon D5100 comes in a close second, while the Sony A580 arguably comes in third. Of these four, the Canon T3i produced high ISO images with the most noise, but at 18 megapixels and a slightly smaller sensor, it's at a slight disadvantage with smaller photosites. It's pretty close between the Canon T3i and Sony A580, though.
Here's a comparison with the T3i's two immediate siblings in the current Canon SLR lineup:
Here, noise performance is very similar, though again the Canon T3i seems to be slightly noisier than both the Canon T2i and 60D.