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.
I think he's saying about only trading. not about storing funds in Poloniex. for the exchange purposes Poloniex is no doubt one of the most trusted platform.. but storing large amount of funds in exchange is not safe.
as a trader you will end up storing something on an exchange at some point. you never go in, trade, go out!
you go in, open an order, wait for it to be filled, it may take an hour or a week even and in all that time your money (bitcoin, fiat, altcoins) are on the exchange and there is no other way around that.
That is true that if you think that without it you can do then i think you will miss the correct price to buy or sell in so many time if you hold the bitcoin in your wallet but it does not mean that you have to keep them in exchange wallet but when you are going to do daily trading then you have to keep some part of bitcoin in exchange and do trading and as soon as you are in profit that time you better withdraw it and just keep small part in the exchange wallet , like this you can lower the loss risk. other then that their is no other way.