On the face of it, someone may think that choosing what varietal(s) to plant a vineyard to is easy: just pick the one that will make the most money and put everything down to that. But that's not the whole story. I can promise you that the many growers who did that with Merlot for a decade regretted it when over-planting and Sideways ruined them. As with any investment, growers should diversify their plantings to hedge against such events.
Furthermore, especially if you are making your own wine, you might want a minimum number of products to be able to offer your customers, whether they are wineries or consumers. You may have a maximum yield you can handle in your winery, or maybe even a limit to what you can get harvested efficiently. Since different grapes will yield at different rates, this can add a wrinkle to your plans.
You may need to limit your allocation to reds or whites for risk and logistic reasons. You will likely have a minimum block size and a maximum number of varieties for your vineyard, in order to keep operations efficient. The considerations are nearly infinite. With that in mind, I created an Excel-based tool to help growers with planting decisions. Check it out. Unless you've used Excel Solver before, you should also download the instructions. They're less than two pages and even an Excel novice should be able to learn how to use it within 30 minutes.
The tool lets you set a wide variety of parameters and place a value on each grape type and then comes up with an optimal mix, within those parameters, that maximizes value. Check it out here.
Song Listened to While Posting This:
Chanson Populaire, Claude Francois