If multiple grape varieties are well-adapted to the soil and climate conditions of the area, the decision must be made using additional components.
First of all, production objectives must meet consumer expectations. The desired outcome, or in other words the finished blended wine, should determine the percentage of each grape variety planted in the vineyard.
Moreover, in the list of authorized grape varieties, it is important to keep in mind that some grape varieties are considered less qualitative organoleptically-speaking. They may not be the best options.
Currently, climate evolution should factor into planting decisions because choosing certain varieties that mature early could have detrimental consequences later. For example, early-budding varieties are at risk of late frosts.
Similarly, the isohydric or anisohydric character of a grape variety must be taken into account, i.e. its behaviour in terms of evapotranspiration during a period of intense heat.