I like slides vs. negatives because you see the actual color of the image in a slide or transparency. And, I like them better for scanning and then printing from a digital file. Of course if you want proofs, negatives provide that much easier than slides. The fine grain of some slide films can make for beautiful large prints from 35mm and medium format can yield impressive results, too. Shooting assigments where you have to get the shot probably is best done with negative materials that have more range for exposure with usable results.