Buy trading platform do you mean for spot trading or for trading derivatives and futures or just an exchange. Personally my favourite exchanges are Binance and Kucoin then Idex for decentralized exchanges. Then you have KoinPro an undiscovered giant.
It’s correct, specially Binance is king in the centralized exchange, mostly big whales focusing in this exchange, that's why i called it’s a rich people's exchange. They have deposit for trading in large scale. Idex is also my favorite in DEX, i stopped using etherdelta since 2018, i'm not comfortable.