JDM von Weinberg , Feb 03, 2010; 08:30 p.m.
The best is probably some truly professional slide scanner, if price is no object.
The Nikon scanners are good. The current crop of high-end Canoscans are good, especially if you're doing larger negatives.
More info on what you're scanning (only 35mm or different formats), how much you want to spend, etc. Would be good. 17x25 (inches?) is big, and suggests you need scans that are at the very least 4000 ppi and probably bigger would be better. I don't think that the scans from the flatbed film scanners are actually as high image quality as the 4000 ppi scans from dedicated film scanners, but they can produce very large files.
Time is another variable, some very good scanners are also very slow scanners.... This may work if you are only doing a few scans, but can be a real bottleneck if you're doing hundreds or thousands of slides, for example. I did thousands on a slow scanner and I would gladly pay $8-10,000 rather than do that again.