As long as you can achieve a sharp focus, there is never a reason to take a shot at less than the maximum resolution of the camera. You're already comfortable with resizing, so capture all the detail possible and go from there.
If I can assume that the lighting and exposure settings were identical in the two shots you posted, note the difference in contrast between the "large" and "small" versions. It's easily seen in the corners of the background, and around "IN GOD WE TRUST" on the coin itself.
Another thing: don't be afraid to post-process the image.I've always felt that there's no harm in enhancing an image
as long as the result comes closer to the true appearance of the coin. Can you see the differences in the pic I'm posting, and is this one a little closer to how your coin actually appears?
