It depends on several factors. In general, I prefer Binance because they haven’t had any major problems yet, they do large volume trades, they have a good trading platform, and they have a decent number of good altcoins.

I also liked using Bitfinex but they stopped allowing US customers, so I had to switch over to Binance.

Sometimes you need to try alternative exchanges to get altcoins that you want because every exchange has different altcoins on them.