DXOMark publishes test results for Canon EOS M. Given that the EOS M uses the same sensor as Canon T4i (also known as 650D), we expect similar DXOMark results for the EOS M as well. And indeed, they do produce very similar results although it is nice to see that it performs slightly better than the T4i. Unfortunately, the Sony NEX-6 appears to be outperforming the EOS M in just about all measurements. And predictably, the EOS M does outperform Nikon 1 J2 which uses a tiny sensor by comparison.
And check out the following – it may surprise you: