Bitstamp, Coinbase Pro & Kraken are the leading exchanges when it comes to fee. Bitstamp is my top pick in terms of exchange fees because they are fee-less when using my personal bank account. I deposit USD into my Bitstamp cold wallet via my Citibank Savings Account and then transfer dollars back out of the account once I need fiat US dollars for trading on Coinbase! This way I avoid fees at all costs.
Coinbase Pro might have better service but they do charge 0.25% for each trade whereas Bitstamp has no trade fees at all! So, for me personally it’s both a matter of deciding which one offers better customer support and which one has lower fees whether your buying or selling cryptocurrency..