In fact, the most secure option is a properly implemented multi-signature online wallet like
www.bitalo.comThere, two-factor authentication is mandatory, so it is secure under all circumstances, even when your computer is fully compromised and the private keys are encrypted with your password and secured with a pre-signed backup transaction you can get the coins out, even when the site is offline or when the database is erased. On top of that coins are covered from loss with 50.000 EUR.
Also, in comparison to all "offline" techniques, you can still use the coins for spending.
Edit: coinbase is NOT 100% secure, because first of all 100% does not exist, also, when two factor is not mandatory, it is easily possible to steal coins via compromised computer