What are some alternatives?
When comparing Poloniex and Kraken, you can also consider the following products
Coinbase - Bitcoin, safe and easy.
Binance - Cryptocurrencies exchange platform
Bitfinex - Bitfinex is the largest and most advanced crypto-currencies trading platform.
ShapeShift - Buy cryptocurrency instantly without the need of an account.
LocalBitcoins.com - LocalBitcoins.com is a person-to-person bitcoin trading site.
changelly - Exchange alternative cryptocurrencies.