If you keep it for a long time, you should create a wallet and store it. If you regularly exchange, you should hold on the exchange
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I prefer after the coin in trading in exchange next store in the wallet that has a sufficient level of security.

You will need both of them, you need exchanger to sell or buy coins and you need wallet to save you coins. If you are daily trader I suggest that you need to have accounts in many exchanger, do not put your entire coins in one exchanger.
why do you need to do it, when one exchanger hacked and you lost of your coins then you still have on another exchanger.
Use your cold wallets for your coins saving.

So far I have had the best luck with wallets. However, if I want to trade or plan on trading anytime soon I will keep in on an exchange. Problem is when you run into things like Binance shutting down for days on end. Really hope this stuff gets more user friendly.

It is believed that the exchange for keep coins is not safe.  You never know what can happen to the stock exchange.  It is most correct to store coins on individual purses for each coin.  But it's very long.  I believe that the main thing is not to keep the altcoins in one place.  And better so - part on the exchange, part on MEV, Waves.  And for coins, which you bought for hold, it is better to have separate wallets.

I stock coins on some exchanges because I'm learning to trade, But I still prefer Wallet..

The main thing is not to keep everything in long bars on stock exchanges and online purses. It is best after the purchase, part of transfer to the desktop purse and save the wallet files, private keys on the flash drive (and preferably two). + Encrypt the USB flash drive.

If you want to trade then obviously an exchange. You want trading in coins on daily basis buy or sell then go to exchange and If you want to hold your coins then obviously in wallet. wallet is safe because u have private key to access.

Use the wallet to keep your coins safe then better if you use Ledger NaNo S which is an offline hardware wallet to ensure the safety from online hackers.You should send coins only for trading because even popular exchanges are now very vulnerable to be compromise by online hackers.

I think it depends on the investment you want. If you want to invest in the short term then obviously an exchange. But if you want to invest long term then wallet is the best choice.