Both still focus on token purchase but the different is instead of the developers dispatching the coins, they give the tokens to the exchanges who will dispatch the tokens to investors.

One thing for sure is that; IEO do not  guaranty that a shitcoins will not go down the drill when the time comes.

The con there is that, (1)  investors will be free from scam developers who intend to steal from them.
2) Avoid littering their identity info through KYC in different websites. Since the exchange already have their information.

3) Since an exchange already have the token, listing won't be a problem. And also you get to choose on which project to invest in since many developers ends up listing coins in exchanges which are not even worth it.

If the token you intend to purchase is listed on Binance, you can take it as an additional plus. *Yet, it's not a guaranty that the coin will survive in the long run.