In summary, in terms of safety level, offline wallet (best) > hot wallets running on your machines > blockchain.info wallet > exchange wallets (worst)
It depends by the security knowledge of the user, a casual Joe with an obsolete Windows OS who installed some cracked programs/games could be the worst of all.
If the guy has a keylogger on his pc, all his bitcoin on a hot bitcoin-qt wallet, blockchain.info and coinbase will be gone very soon (assuming he has no idea what 2FA is).
