The 6D has a "full frame" sensor - physical dimensions are close to the 36mm x 24mm size of a 35mm film negative frame.
Both the 7D and 70D have APS-C sensors - physical dimensions are close to 22mm x 15mm and close to the same size of a negative frame from "Advanced Photo System - Class" size film.
While the 7D and 70D have sensors which are roughly the same size, the sensors themselves are very different because the 70D has the new dual-pixel AF technology.
- I was just going the info at BHPhoto which states they both have 20.2MP CMOS Sensors with the 6D being full frame and the 70D being APS-C. In any event I would still like to have an answer to my question.
That's the number of pixels, or the resolution. But as Tim stated above, the 6D sensor is significantly larger, hence the much better high ISO performance. Althought the 70D has new technology, I don't think you'll see a marked increase in high ISO peformance over the 7D, and it won't be close to the 6D.
12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.