Eating spinach raw isn't a bad thing, and SFGate.com says eating it that way makes it "significantly higher in folate, vitamin C, niacin, riboflavin and potassium" than cooking it. That said, cooking spinach "provides greater amounts of vitamins A and E, protein, fiber, zinc, thiamin, calcium and iron." The benefits don't stop there, as sautéing it "helps free up some of its most important carotenoids for absorption", like beta carotene and lutein, which could help ward off vision loss.
Kale has plenty of nutritional benefits however it's consumed, but cooking it increases its iron content. And although it has the same amount of calcium cooked or raw, "to increase the amount of calcium the body absorbs" (emphasis ours), Chron.com suggests pairing it with a calcium-rich food like mac and cheese. Or using it to top a whipped ricotta pizza.