It really depends on which part of image quality you're looking at. My 1DsII will blow away my 7D in terms of high ISO noise, despite the age. Aside from the recent full frames, I haven't seen much noise improvements over the years. All the crop bodies have been pretty similar in terms of noise, I think. If the 70D has similar noise levels to the 7D, you should see less noise on the 1D until ISO1600.The larger pixels on the full-frame means slightly soft glass will appear sharper on the 1D. Chromatic aberrations on the 85mm f/1.8 will appear thinner and be less noticable. Your 1D, being a 1.3x crop should see some benefit from all these areas, but not as much as a full-frame camera. But high-quaility full-frame compatible glass is expensive. A lens that appears fine on a 1.6x crop body may have sharpness and distortion issues near the edge of the frame when used on a 1.3x or full-frame body.
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