The safest way is hold in wallet. But if you want to trade frequently, dont need to hold it in wallet. My coins that use for trading are holded in exchange.

maybe for my own right now I prefer the stock to store altcoin that we have and of course altcoin must have high security level with so tokens that we have will be safe.

This is a rather difficult question and I will explain why. Many people know that the last minus 10 percent was caused by the hacking of the Chinese exchange and theft from there a fairly large number of funds and this affected the rate of both Bitcoin and many altcoins and the crypto-currency market fell by 10 percent. That is, to keep money on the stock exchange does not seem to be the best solution, because there are many security issues. On the other hand, wallets are also not so secure, because we've all heard about hacking MEW  and today MEW is the best wallet and I'm sure that this wallet is available for every participant of this forum.
The best on reliability of a purse which now you can buy, it is a hardware wallet. For example, I use the hardware wallet TREZOR, but in the use of this wallet there are nuances, as it is designed only for a certain number of coins.
As a result, I think that it is better to store money still on the wallet, but on the other hand more profitable and cheaper coins can be purchased on the exchange, and the reliability they are approximately the same.

Well wallet is yours. exchange is theirs. no, although they want you to believe that so you keep your shit with them. thus, exchanges will call its app a "wallet"; but you need to understand keeping bitcoin in an exchange is not keeping bitcoin/Eth in your custody. On the other hand, Mycelium, Jaxx, Samurai, Electrum, Ledger Nano S, Trezor, and paper wallets: these are all personal wallets in which you own, hold, possess your keys.

So yes I prefer my wallet.. I keep it safe with hardware wallet

I agree! Everyone knows that you own a crypto currency when you own a private key. Thus, when you store money on the exchange they own your money and this is not a reliable way of storage. On the other hand, if you are actively engaged in trade, then it is not convenient to constantly transfer money from your wallet to the stock exchange and vice versa.

I think if you hold the coins for the long term, so I prefer you to have used the wallets. If you want to use the trading so defiantly you have to go to the Exchange.

at this stage of market is in very dump condition so hold the investment....its all depend on your mind ...how much risk you can bear ...so i recommend you hold it

Of course, it is better to keep your coins in your wallet, if for long storage of coins. Although it's up to you.

It depends on your coin turnover. If you constantly make some operations with your cryptos, it is better to save it in Exchangers. But I advise to use wallets for large amounts of coins.

I prefer to keep all my coins in exchange but not in 1 exchange, at the moment i used 7 different exchange just want to be more safe, because keep all money in 1 exchange is risky, and by keep in different exchange i can trade it for day trading or swing trading in efisien. Although keep in exchange more risky than in wallet but my purpose to get profit from trading.