600d vs 650d high ISO noise
I can't speak to DPReview's tests (since I wasn' there), but the images weren't shot at the same time, nor were they processed identically. There's always a large margin of error with this kind of testing, so take them with a grain of salt.
Here's a previous discussion on T4i vs T3i with some of my thoughts...
Good judgment comes from experience.
Experience comes from bad judgment.