I prefer the action I get by bending them when I am jigging them vertically, whether it be on open water or through the ice. I pour them, bend them, and paint/seal them.
If I'm casting them and ripping them back to the boat I do not bend them. I think ripping them, especially in current, while casting imparts the dying baitfish type fall to a bait that I'm looking for. I really like the casting spoon lure for this particular application as well.