Update: as reader Eyal (thanks) correctly pointed out in the comment section, the credit for the images used in the comparison goes to imaging-resource.com. Apologies for not having seen it.
It is interesting to see how much sensor performance went to the better for APS-C sensors, especially for higher ISO settings. If you compare the crops shot at ISO 6400 you can clearly see how much better the EOS 70D performs if compared to older models, the 70D outperforms even the 7D. Differences appear to be less obvious for the full-frame DSLRs, though the improvement is visible.
Although you have to deal with automatic translation the post is definitely worth to have a look.dslcamera]