We're really talking about color neg films which cannot be readily examined right atop a light box after processing like chrome film can be, but which must jump through intervening hoops to analyze - whether a proof print, or a scanned viewing option.
And the notion that Portra will yield the "best reproduction of difficult colors" is vacuous - which Portra, which difficult colors, what do you mean by "best", and what on earth do you possess as real evidence behind that statement? Yes, the Portra lineup has solved some of the color repro problems characteristic of earlier color neg films, but has inherited others, deliberately. It's just another stage in the evolution of the same things. And only Ektar realistically fills in the gap between that and what chrome films do way better. There simply is no silver bullet.
If you need to reproduce very specific hues, test, test, test film, and then after going insane trying, and sitting on the porch of the insane asylum in your rocking chair, with a set of watercolor pigments for therapy, you'll finally realize you should have been doing it that way all along. In my case, I go insane either way, so it's easier to blame the camera and film than my own direct mess. But I'm obsessed with capturing and rendering certain complex hues in nature.