I can't pretend that exchanges are better than hardware wallets, because there wouldn't be any points for me to defend that. Although having your coins on the exchange can make trading faster, but that risk is not worth taking, except maybe you don't have much coins to hold, then you can go ahead and leave them on an exchange for easy trading when you want. But if you're the type that has lots of coins, then storing them on an exchange is the worst move you can ever make.