Buying from ICO is far more profitable, because it gets discounts and other bonuses, but can also pose a risk of large losses if the number of coins we buy has a low price on the market or is not even listed on the crypto currency market. When buying through exchange we can see price movements and ensure the price of what we buy and then make a choice to sell when making a profit, of course buying through exchange we have seen with certainty that the coins we buy already exist in exchange. I prefer to buy through exchange, and make sure to buy when the price goes down and will sell it when the price rises.