i would plant both, plant the sugar beets in the sping , and turnips in the fall. you can also plant some winter wheat ,the deer love the small grass as it is coming up.
i would try a strip of this and that to see what they want. and watch it if you can during the off season ,this can really help for fall planting , but i find soy beans are the best for a late season food plot.
take your kids hunting and you wont have to hunt your kids.