My vote is for paper wallets where you have multiple backup copies.
Online accounts like Mt. Gox and Coinbase are my absolute _last_ choice. The former went out of business, the latter ate their customer's value in bitcoin cash. That's a hard veto.
An electronic wallet can be lost to a cyberattack, hardware failure, or I could forget the damn password. If I'm smart and write down the password and keep backups and never connect that system to the internet then I can avoid those. That is all more complex than a paper wallet.
You might talk me into a multisignature paper wallet, with the keys stored separately in audit-able tamper evident ways in secure locations. I'm hesitant about that though, since loss of n keys can cause the entire sum to become inaccessible