I think it is best to keep your funds in your exchange wallet . Tho you should be careful on which exchange site you are going to store it . Make sure they have a good reputation or background on their security . I mean , no history of being hacked for long term . It is good practice to keep your funds in exchange site if you are a constant trader .
Keeping it in the wallet - This is good only if you want to withdraw or convert your balance into paper money . I mean , wallet can be stolen . hacked . If you have a hardware wallet then its the best option if you just want to protect your funds .
So it still depends on what purpose you want . If your a trader then keep it in your exchange wallet , because if you keep transferring your funds into your wallet , problems may come up like slow/high transaction fees . And during dips , you need your fund to be readily available always . On the other hand , if you just want to secure your $$ then like i said a hardware wallet is the bext option for that .
This is a somewhat self explanatory exception to holding coins in a wallet you control. Of course if you trade frequently, then it makes sense to store your funds on an exchange - it's the only way you can trade on centralized exchanges and the risk of the exchange disappearing with your funds is one you have to take into account as a trader.
The alternative is moving to a decentralized exchange - where you can still trade but control your funds.
