7:22 PM
When comparing a 1DsMkII vs 60D with regards to resolution only, it's more complicated because of equivalent framing. I think a correct model would basically take the pixel spacing of one sensor and transform it using the relationship between sensor sizes.
While one could do this, things like dynamic range, color depth, and noise performance are more important to me (and are usually not equal as my aforementioned model assumes). These qualities usually go up with a larger sensor as it will be capturing more light, but technology improves as well.
But yes, all things being equal, an 18mp camera will produce better 4x6, 20x30, 4mp, 8mp, and 12mp, etc. photos than a 12mp camera.
As pointed out by the graph in my comments with Karel in the other answer, resolution is most often limited by lens quality. In the end, resolution all of todays DSLR sensors is excellent for large prints when paired with a good lens.