The seedphrase will not help you protect your wallet against unauthorized access (unless you add a passphrase to it, but neither wallet supports that). It will just help you recover your funds.

As mentioned above, both wallets are closed sources so there's is no way to know for sure, but assuming both of them are being honest, Exodus might be better if you trust your ability to keep your machine safe since Blockchain does keep a backup of your wallet in their servers.