Most of the exchanges have been having some sorts of problems and they can be hacked. Despite that you can keep some for trading but not a large amount.

I think it really depends on some factors. If you want long-term holdings, I suggest you keep it in a private wallet where you have your own private key or wallet seed stored somewhere safe.

However, if you want to do day trading of your crypto assets, you should transfer them from your wallet to the exchange platform. It is not recommended for us to store our long-term holdings to an exchange (like what Etherdelta and a Japan-based crypto exchange was hacked a long while ago).

Again, it depends on you as long you are responsible for your risks.

For more security you can buy a hardware wallet, such as Ledger Nano S. It`s way more secure than keeping it in exchange.

It is always better to store your coins on wallets rather than preferring online exchanges as there is more chances for losing of your crypto coins if your store in online exchanges, it is true that exchanges can also act as a wallet but it is not at all safe for storing crypto coins. One should always keep in mind that they should store crypto coins on their hardware wallets or USB wallets which is more safer than storing on online exchange and online wallets. Paper wallets are also safer to use you can print the private key and wallet id and should keep in mind to secure the printed private key safely without sharing it with any one else as you might loose your crypto coins if you hand over the private key's or if you loose your private key print. Paper wallets cannot be hacked and so it is the safest of all wallets.

i like wallet, it is safe and save me from trading temptation. but it is depends from what you need, if you do trading you can put it on exchanges, if you do invest in long term you can use wallet instead.

It is best not to keep money in one place, decentralization should be decentralized. Keep some money on the stock exchange, some of the money on a cold purse. Situations are different, hackers, special services, scammers. You need to be prepared for any situation.

for security i think wallet, but for profit i think exchange. because if you put it on the exchange you will easily invest it

I think the most important is the wallet or exchange site is trusted or not. you can know it by looking at many things. such as having a clear owner, having a verified business address, having many users, having a long life, and etc. I'm an active trader. so I would rather keep my coin in a exchange sites. Yeah you know because it's easier to do convert and exchange with other currency..

be careful from exchanges, I use exchanges only for change or trade with very low amount of my assets. some of them after some time be scam. so check and be careful