When it is for a long term store, it is more advisable to use a hardware or paper wallets, where you are in full control of the activities done. If it's an online wallet, it can't be fully trusted cause you are not fully in control of your coins.
For long term a hardware or paper wallet is the best options. For any other activities, a wallet like Electrum, which gave you total control of your private keys and the ability to adjust fees plus the security you can have is most trusted. It good to store a few bitcoin in a trading exchange, but just for your trading purposes only and don't put everything in there.