There are several reasons why Binance stands out among major exchanges right now. It has lowest maker/taker fees for starters (just 0.10%) which could be further reduced to 0.075% by using native Binance currency i.e. BNB for fees. Kraken and Bitstamp have relatively higher fees. Although these percentages may look minute but can become important factor when doing margin trading. Apart from that, the volume on Binance is higher than the counterparts which means lesser spread between buy & sell orders. It also means faster order filling.

By the way, I don't think Kraken/Bitstamp have better rates than Binance. In fact, Binance's prices are more close to actual price due to larger volume. However, all these Exchanges are reputable and you can choose any depending upon which deems best for your needs.