Encryption isn't the concern with these scenarios. Security isn't just about encryption. Hardware changes and allows faster cracks, access to a file can allow deconstruction in some circumstances. Most people who get access to your file will likely not try to crack it at all, unless you're someplace like a convention for people who crack things.
With good local password managers, this ultimately comes down to the physical security of the file, the passphrase you choose to lock it, and how you store that passphrase.
Once a file has been copied out of your control, it is only a matter of time before the file is cracked. Especially if you use similar passwords across your accounts and any of those passwords have been compromised. An example might be locking the file with your Facebook password.
If you opt for anything simple (fewer than 10 characters) in regard to a key, and guessing the phrase using a dictionary attack built off of you on a profile could be cracked within a couple of days for someone who knows you or is really good at building profiles if you randomize characters. If you don't, it could be a couple of hours. If you choose something completely random, like an SHA1 hash for a password, you'll likely not remember it, and in this case, that password will be stored somewhere else, either in a text file on a phone or another easily accessible device. Ideally somewhere like in a fireproof safe would be ideal. If you do use a hash for a password you can always recreate the hash by hashing the phrase you used again. If you're known to do this, then good crackers will attempt cycles of your own personal dictionary through a pattern of hashes to make a custom rainbow table. This can come down to social engineering and whether you've told anyone about your "mad skillz." I overhead an employee bragging about their use of this very method and got their password in 15 attempts.
If you store the password in something like the Mac Keychain list (if you're on an Apple computer), the attacker only needs to capture your user password or use an app to steal it. There are often ways to do this sort of thing.
Otherwise it becomes a matter of convenience in regard to cracking your own password to get back into the password list if you manage to misplace the password or if you forget it altogether.
If you delete all of your other records of your passwords and store them exclusively in this file, now if you do happen to lose the password, it's really secure because nobody knows the password. I can attest to this account, as I myself have been barraging a 256-bit encrypted DMG where the password was misplaced for over the last few days for a client. It could take weeks in this case and we have a 1000 word dictionary of core possibilities.
The local password managers however are likely safer as they require access to your encrypted file, whereas in regard to remote password managers the network connections and encryption methods being used throughout the chain have to be solid with no chance of a man-in-the-middle attack.
If you use a local password manager and lose the file, corrupt it, or lose a drive you have no way to recover if you do not have a backup. Physical security of this backup is important if it contains your password file. Why an attacker go to the trouble of trying to get into your Windows machine if they could clone your external backup drive and access the files at their leisure? You'll want to make sure these backups are encrypted as well.
All of these come down to whether you really are a target or not, for most people it would have to be a personal attack for someone to want into their social media accounts this badly.