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No exchange is 100% secure even if claimed by exchanges. Once you withdraw your coins to an exchange, the coins no more belong to you because you no more hold the private keys. So, it is always better to just trade them ASAP and withdraw to your local wallet if you can and if transaction cost allows.
It would be even better never to transfer coins to the exchange at all. If the exchange functions are built into the wallet. Perhaps in the future it will be possible.