I just sold half portion of my ETH Investment.
I have not used poloniex or Kraken!! I have used
ETH2USD because they offer INSTANT payout.
Anyway i have bad feelings about poloniex, just be carefull.
It's a brand new site never read it anywhere here,you're lucky to cashout do they have a thread here,if they have not yet I wouldn't deposit my ether here,it's much better to trade on Poloniex in my opinion..