I havent tryed to use offline wallets at all, i do use my bitcoins as i get them in the general, always looking for a place to invest my coins. Online wallet the only i do trust is blockchain.info, soo far an amazing service being provided by them, and now we can get ethereum as well, the only change i didnt like were we need to pay to moove funds inside the wallet as well cant sign more message with new adress. A lot person i do know does store their coins into offline wallets, because they have a decent ammount soo they need to take care of them.
wallet is able to store your high amount of bitcoin for a long time and also no one will able to hack your amounts of coins and which will be very easy for you because also this can be tore for your future. And about online wallets is also good because if you are a person who trade daily and sell or buy bitcoin daily then online wallet will be perfect in this term. According to me both are really good and pays important role in investment of bitcoin because offline