If you need to scan negatives, verify this feature is included. This is often a subjective topic. Image quality consists of resolution, unsharp masking, dynamic range, color accuracy, gradation. These are the things that are characteristic of a scanner. In other words, we can't change these fundamental characteristics with the software.
Some optics are of better quality and design than others.
The unsharp masking circuit is critical determinant of image quality. This has a major impact on detail. For large scans, a scanner that produces high resolution at true optical resolution will produce smoother scans with better detail. Drum scanners can unearth a lot of shadow detail at times not even readily visible on a transparency to the naked eye. They can reproduce a wider range in original density from a piece of art.