If you are looking into long-term investment, then Wallet and (preferably cold storage) is better.

On the exchange, you only keep amounts you want to trade. Not more. Or the amount that you actually want to pay out.

There is at least one article on news that exchanges have been hacked. I don't like paying Gas for transfers from exchange wallet to my private one, but this is the only way to have them safe. In my case for the last three months its 100% on wallet.

I am looking into trading and investing now, so most likely will be transfering either onto Hot Wallet or Exchange, depending of what I want to do.