We picked ours based on group (family) decision. We are in an AVA in southern California with quite a few other small commercial growers in the area. There is at least 25 years of evolving information and taste as to what does well here. There were three main considerations for us. 1) Our varietals are appropriate for the climate (high Winkler III or low IV -- we can have long hot, dry summers here) and soil type (not much organic material; decomposed granite). 2) Decent/appropriate buyer demand from local wineries. 3) We had to care about the varietals -- are they interesting to us, and will we care and be passionate about these grapes growing these grapes?
We all like the Rhone varieties, and in general we like dry, crisp, fruity, flinty or complex whites, and bigger, or at least challenging reds. We selected Mourvedre, Sangiovese and Barbera for our reds, and Roussanne and Vermentino for our whites. I produce about 60 gallons of household wine a year (last year one rose, two whites and three reds), and the rest (95%+) gets sold to wineries. We have about 7 acres.