You don't mention what sort of image you're scanning and how you're printing the image. Is a photograph or a slide? Is the printed scan going to be larger than the original?
The scanned image at a higher dpi will be better as a computer file.
When printing the file, the deciding factor is both the scanned dpi up to a certain point, the printer resolution, and if you are enlarging the image. Many printers are 300 dpi, so scanning at 1200 dpi won't necessarily give you a better printed result if the original and printed product are the same size. If you're enlarging, then you need to do the math to see what resolution you need to scan at.
Of course, you can always scan at max resolution and you'll always have the best result without trying to be fancy.