I think every thing has its advantages and disadvantages. If it was me, I would choose to keep them in wallet. Because it is absolutely safe and no one can know it. However, if you keep them on the exchange, you can freely trade whatever you want. That is the advantage of it

In my opinion it's not the best idea to keep all the money in only one place. That's why i prefer to keep tokens on several wallets and also on several exchanges.

If the investment is a short-term investment, you can keep it in a stock market account. Staying in your wallet is more expensive than trading. You must pay commission and transfer fee. Long-term investments should be in your wallet, safer than exchanges

To trade every day, I use the wallet exchanger because it is not convenient if using a wallet for each coin. for long-term investments, I use a wallet for every coin.

This theme is totally dependent on your demand, At first, you have to think what you want to do?
If you want to trade then you have to take an exchange. on the other hand, If you want to hold then wallet is best as you have total control over your assets. One thing you should know that You have an access to any wallet and you can send or spend anywhere you want.

All life is a gamble, so you can not know in advance what the best decision is. In these cases it is better to separate the investments anyway.
Cold wallets are certainly safer, but they are static and produce nothing.
The exchanges are always at risk, but it is the only way to trade.
For prudence, it is good to use at least two or three exchanges.

On the exchange of course you can store money, but I still think that it is better to store your coins or tokens in your wallet, as this is a more secure way to save your funds for a long time. So clearly keep the money in your wallets.

I would loose all my passwords in the case if I will have a new wallet for every new coin of mine, lol! imagine that quantity

Everything is very simple. The coins that I trade are on the stock exchange. Those that do not trade are in the wallet. It is better to keep your coins for retention on your wallet.

main reason is safety. If you have your coins in wallet where you have access to your private keys, no one will enter it except for you. When you hold your coins on exchange, you need to rely on them