I think you should ask people to talk about their experiences in every exchange they use.

For example, poloniex is good exchange because it is easy to use, but has bad support and has people who lost money

Bittrex also have case of bad customer service

Coinbase also has its problems

Bitfinex also has its problems

There are GDax and Kraken who do not hear a lot of people complaining.

All exchanges you mentioned have good trading volume