Is it better to freeze raw, or to cook/overcook before freezing to keep food from spoiling too soon?

It totally depends on the food and if it was frozen before. Even different vegetables react differently to freezing, so it isn’t a ‘one solution fits all’ situation. Your question, as it is, is unanswerable. You’ll need to ask in relation to specific foods. And it isn’t spoiling you need to worry about in the freezer. It is freezer burn, crystallisation and bitterness. You need to blanch almost every vegetable, not cook.

@ScienceChick Thank you. By the way what shouldn’t blanch, and why?

Vegetables like beans, peas, broccoli, cauliflower, asparagus, carrots, and Brussels sprouts, be sure to blanch them first.
When it comes to leafy greens, like spinach, chard, and kale, the choice is yours. You don’t have to blanch them, though if you do the greens will cook down and won’t take up as much space.
And certain vegetables, like tomatoes, potatoes, and winter squash, for example, don’t need to be blanched before going into the freezer.

@ScienceChick Is blanching for killing whaterver can make you sick? What is the other purpose of blanching?