there is many online wallet are available to store your bitcoin but i usually use online wallet to store my bitcoin in the blockchain wallet i feel that blockchain is much more safe and secure than other wallet so i prefer that blockchain is better and simple and easy.
Yup blockchain wallet is really better and safe in compare to other wallets as it gives fully security features to the users and if you don't have much bitcoins then its better to go with a single wallet but people who holds high amount of bitcoins will never depend only on single wallet and will prefer to store their coins in different wallets to avoid the risk of loosing them.