Several of these films are popular for a specific application. Velvia 50 and 100, for instance, are some of the most popular landscape films because of their dramatic colors. Astia 100F is known for producing great skin tones and portraits. So, for many of these films, special versions were created to "tune" the look of the film to their common applications even a bit more. So the Landscape versions of the Velvia films will have even darker skies, richer oranges, etc. The Portrait versions will have lighter skin tone and a color tone that favors portraits, if necessary.
Be sure to watch this great walkthrough video on VSCO Film 04 here: http://vsco.co/blog/vsco-film-04-walkthrough-video.
Feel free to contact firstname.lastname@example.org if you have any additional questions.