This is not meant to be an exact statement, but negative film is a bit like log recording whereas slide film is a little bit more like linear recording. With a good enough scanner you can recover highlight detail from negative film that you cannot recover from slide film. In other words, you can expose negative film for the shadows and not worry about losing highlights, since many negative films have many stops of highlight latitude (HDR is built into negative film, so to speak). With slide film, if you expose for shadow in high contrast scenes you can lose highlights irretrievably, which is why if you look at the work of some of the greats using Kodachrome, for example Alex Webb's, in high contrast scenes their shadows can be pretty black and lacking in detail because they chose to have good highlights. It is a fine and beautiful look, though, nothing wrong with it, but it is a choice forced on you by slide film and not necessarily by negative film. You can do that also with negative film (Ansel Adams used negative film but increased contrast and burned (darkened) shadow areas to black in many images for drama) but you don't have to make this choice at the time of shooting (or at all) as you do for slide film.
As for color casts, you can correct that during or after scanning, just as people needed to do color correction on wet prints in the olden days. Color negative film in fact doesn't have a set palette; you decide that during printing, so there isn't really a Portra "look" set in stone, just whatever many scanners/printers chose as a default palette, and many people edit Portra images into something entirely unique to them (the Reddit analog forum has many examples of this kind of thing). The same goes for scanning or printing slide film. While the projected slide itself with a given temperature light source is a reference point, you will often see many different color interpretations of the same famous Kodachrome slide image in different prints. Do a google image search for Joel Meyerowitz and you will see what I mean.
