Diversity is always best when working with plants. There are so many varieties available now that you could hedge your bets and have some that are more drought tolerant, some perennials, and some annuals. This also spreads the work out so that instead of working the whole field every year or every 3-5 years you could do 2 acres a year or any mix you choose. This spreads the planting cost and work over time instead of all at once.