The availability of exchange is worldwide and mostly in the US states. The main advantage of Kraken is its fame. It comes in the top 5 or top 3 most popular Bitcoin exchanges. Its diverse range of trading pairs is another advantage. Similar to other large exchanges, it has good liquidity in some lesser currencies. It has specifically good liquidity in the BTC/JPY pair because of many Japanese traders to Kraken from Mt. Gox after the hack.