Now that there is more detail from the OP, I will suggest the following for making lithographic post card prints from 35mm film:
Kodak Portra 160NC and VC for the highest technical quality, but you will likely need a tripod, so will need to not be lazy.
Kodak Portra 400NC and 400VC for if you are lazy or in a rush (don't want to use a tripod), and don't necessarily want or care about the highest in technical quality (which you certainly do not "need" for lithographic post card prints).
If the goals were more "artistic", I would suggest to use the one that will create the images that best suit your concept, and would also assume that you care enough about them to not be lazy or in a rush. Since these concepts and image styles may vary from project to project, I would thus suggest getting to know all four of these films for personal "artistic" use.
However, your aim is commercial. You aim to create and sell small, relatively-low-quality lithographic post card prints. Personally, if using film, I'd go for the two types of Kodak 400, get the shots done quick and dirty, without a tripod whenever possible, and be on my way to go shoot pictures for myself that I actually respect. To tell you the dirty truth, I would personally use digital.
NC subdues contrast and saturation, and VC exaggerates it. Kodak is very nice in offering us both NC and VC emulsions in both medium and high speeds.