The A70 offers a large amount of valueable features for the money.
Nikon 3100 IS a good camera, but no manual focus, no Aperture priority, no Shutter priority.
The only major complaint about the A70 having 'soft images'.
For someone who wants to process their images, A70 pictures respond very well to sharpening and contrast adjustments with an image editor. Canon could have done what other companies do, and over process internally. Good thing they didn't. It is much harder to process an already sharped image than one that has not. There isn't anything wrong with the optics, or processing, it is just different to what people are used to.