Sunflowers need less moisture but don't stand well during the winter. Check out Uguide's food plots in the snow pictures, how well they still stand. Our research (which is not scientific and sometime done over adult beverages) shows milo, corn and cane to provide the best over all food plots even when moisture is low. Milo will still generally get heads big enough for food plots. The years we used some sunflowers they got knocked down and cover in snow early and where of little value. For what it is worth birds seems to like this order:
Beans, sunflowers, corn, milo, ... but winter cover and shelter from ice or snow showed us
Milo, corn, sunflowers, beans.
If you want a full scale explanation, PM me.