I think it all depends on your goals,for traders is better on the exchange, and for holders of course it is better to create wallets, since the exchange is not insured against burglary. I have such an opinion.

If you don't want to waste money, you must keep crypto in cold wallets. Maybe exchange good way for easy and fast to use. On exchange just keep a little money, which you need for transactions.

It depends. If you want to trade then it's best to put your holding in exchange. But if you want to hold you coins then wallets are better. But if i we're you I won't put all of my coins in individual wallets or put all of them in exchanges. I would rather divide them almost in half. Half for exchanges and half for wallets. But then again that is what i would do so i could diversify my coins. An important thing to remember is to really research your wallets or exchanges, I've hear of people having troubles pulling our their earnings

use both is better. if you just hold coins for short term I think it's no problem to hold in some trusted exchanges to shorten the time so you will never miss a golden opportunity.
and also hold on wallet with private key for coins that you dedicate hold for long term investment.

Don't put your digital currencies on crypto exchange sites. Only use this crypto exchanges when there is a need to exchange your digital currencies. If you only know that there are many cases of crypto exchanges accused of being a scam or got hacked. It's not so safe to put in all your coins there. So use wallet instead of using the former as your digital currency storage.

I think putting token or money in a exchanger is dangerous. Because  many hacker targeting a exchanger than a wallet. Because exchanger has more money than a wallet. Thats why i choice wallet and if you choice wallet you can transfer your tokeen anywhere exchanger..

for now, I keep the coins I have on the exchanger, and that's more practical. although it's a big risk if it's hacked, but, that's practical. I might save 30% in the exchanger, and the rest in the wallet.

Exchager wallet is not safe. If need to hold coin. You the wall it safe for your coin. But you not some information to other people. It safe for your wallet. If want exchange you charge the wall to exchange wallet. But if change the coin. You know the process before use. It any time to change the price. So check the price day by day. Then you get some ideas.

Basically for me personally I don't too concerned about exchanger site for my wallet especially for my btc, i'm more prefer to a wallet site to pick for my wallet. And often I keep some coins besides btc in some gambling sites than exchanger site. But maybe someday if I really focusing some of my coins (altcoins) on trading., I might choose on the exchanger site.