I think everyone here will have different response on this inquiry. Best exchange is the market where your comfortable to use with and even the benefits of exchange favor your needs. Usually some will say they like for example Binance, some uses Kucoin, and other's prefer bitmex. Depends on the coin you wanted to trade or the fees youre looking into. We have different perspective in trading like me. I like market with easy access and have stable volume and liquidity. Binance I use this for different margin trading and I like the set up of trading when I am using bitmex platform. It's totally up to you mate.