Keep altcoins in exchanges only if you are planning to trade it at the earliest.  If you are planning to hodl your altcoins for long term it is better to keep it in the wallet. For safety reason, it is advisable to keep your altcoins in more than 1 wallet j

I always keep my coins on my wallet, when I sell, I sell to my real life friends
They get hooked too fast

One can store in both exchange and personal wallet it just depends on your specialization.
For day traders I think storing on exchanges is the best for easy transaction, but for long term investors it's better to store on personal wallet.

Best to keep your crypto spread across several exchanges and wallets.

I would not prefer my long-term hodling into an exchange.  I would rather keep is safe in my hardware wallet.  But for my short-term trades, I would never take out from exchanges.

To my knowledge there are wallet-based ethereum tokens such as Myethereum wallet and wallet based waves token in Waveswallet here is usually a temporary wallet that we can use before the coin entered the market and after entering the market can be moved to the address wallet in the exchanger. And for security may also use the wallet recommended by the coin developer.

The cons for the both is risk of loss due to hacking activity of hackers. If you keep your coins with the exchange and there is hacking issues if the exchange were able to recover some of the funds you will be able to get something back but if it is in your own personal wallet and the hackers attack you may lose all without nothing recovered.

It's up to you what you want. If the coin has grown then change. If the coin is worth a penny then leave it and wait for it to grow.

I don't know why, but I like to have all my funds in one wallet, and so, even when I trade my coin,s I would withdraw from the exchange to the wallet!

It all depends on whether you are prepared to lose your coins under a force majeure circumstance.

If a VERY LARGE amount in the crypt, it's better Wallet.