Bittrex shot itself in the foot when it froze lots of accounts because of some sort of "KYC" issue, or so they said, and did an abysmal job of trying to sort out the mess it caused (which I think is still not fixed).
Binance looks to have managed a good job of customer support, unlike some other exchanges, and this is what sets it out above the others.
At the end all of these exchanges will pull the "AML/KYC" rabbit out of the hat and freeze accounts. Exactly why these exchanges will do it is open to suggestion because some do it for selective scamming and some maybe for genuine reasons related to law enforcement agencies requesting it.