As been discussed many times before using a Brainwallet is a bad idea.
I disagree, I have never lost anything from a brain wallet but I have lost quite a few coins from failing hardware wallets and dying hard drives.
I have to agree. It would appear to me that your Brainwallet will be as secure as the passphrase you used to create it. So if you choose a very difficult passphrase your brainwallet will be secure. I would assume it's the same as choosing a passphrase for your encryption vault.