Online wallet helps you make it easier, you can make fast transactions, bitcoin payments and other types of cryto currency.
However, I noticed that online wallets of many people have problems related to security, hacking and theft
Wallet offiline helps you to store your bitcoin more securely, people often store large amounts of their cryto-money assets here and for a long time.
Both have its own advantages and we cant neglect importance of anyone so if one wants to get connected to world and do buy and sells through bitcoin I recommend online wallet and it is best and if one wants to simply make collection of bitcoins then the best one is offline no one will get access to any one of them so use them without fear.