There must be pros and cons, but in general, would you recommend them?
and pls tell me the reasons why !?
The hardware wallet like the ledger nano is a must buy for any crypto investor. Your private key will never leave the hardware wallet so you don't have to worry about it being compromised. And if you ever drop the hardware wallet in the swimming pool by accident, don't worry. When you set it up, you will get recovery phrases that you write down so you can open your wallet if your wallet ever gets damaged. I know they average around $100 which seems pretty expensive but the purchase is worth it.
Only leave coins on exchanges if you day trade but never leave them there long term because exchanges can be hacked and you can lose all your coins.