Coinbase isn't very safe, if you ask me. Use bitcoin-qt or electron. Pretty much the best out there. Only just coinbase if you're poor and don't have anything to lose and you want to use them so they can post your transaction fees 
I never keep over a bitcoin in my coinbase account, let me tell you that.
I never keep over a bitcoin in my coinbase account, let me tell you that.
AFAIk coinbase is safe enough as an exchange, because they have insurance that cover your funds, not like other exchange, and they are directly regulated with IRS
so if you really want to store online, they should be your first choose, betetr than blockchain.info for sure
For an online wallet like Coinbase, up to 1 BTCs would be a maximum that I would store in it. 1 bitcoin is not that much of money and for some non-technical people it's much easier to just leave it in Coinbase than to go through all the trouble of learning and setting up their own wallet.
As long as you don't send your funds to the online gambling sites, etc, Coinbase is good enough I guess up to 1 BTCs.