If you are talking about speed , then it should be Binance.com
Binance seems the most popular place for trading. But, unfortunately, it is not allowed for everyone. For example, here in Serbia I can't register there, they just have not an option for registration for my country.
I think that one of the problem with almost all exchanges and not only Binance. Most of them involve the geographical restrictions because of the government policy of different state. Every good exchanges are expected to comply with the law of states, aside from the state they are staying on. So, the same time, it's not their fault.