I would choose Poloniex anytime , Its secure as most of the funds are stored in cold storage , It has the biggest trading volume If we exclude the Chinese exchanges , It's fast , and also have good design and a good support. I don't see a reason why I would choose another platform.
It is secured until it's hacked.What makes you think if they are hacked by the internal team or by random hackers,your money would still be safe ? IMHO,do not trust any trading sites with the money you can't afford to lose.