Sprouts do contain more nutrients when raw or not fully cooked.
But when you cook the sprouts you kill off any potential bad bacteria that could cause you an illness.
Sprouts should be cooked especially for elderly or children or anyone with a weakened immune system and I would always cook the sprouts anyway because they are still healthy when cooked and you avoid getting sick.
As long as you're in really good or relatively good health then eating raw sprouts or lightly cooked sprouts is okay but the older people and children should really only eat cooked sprouts due to the bacteria that can be in the uncooked sprouts.
Sprouts are more nutritious when eaten raw but when eaten cooked the sprouts are still very nutritious as well.
I prefer my sprouts cooked anyway because cooked sprouts taste better and are easier to chew than uncooked sprouts.