Is it safer to use a PGP key encrypted with a password than just the same password separately?

I'd like to encrypt some master passwords that I want to store with added security outside of KeePass, instead as just a normal record in the database. I was considering storing these passwords in an encrypted RAR file, but now I think that could not be a very good idea since it could be possible that there is some bug/backdoor in the RAR library that could make cracking it easily.

I'd like to consider encrypting the master passwords with GnuPGP (AES) with a combination of a key instead of plain passwords. Now I'd like to know if it would be more secure to encrypt the master passwords with the key instead of with just AES and the password. Because wouldn't it be more resource intensive to bruteforce an encryption key to retrieve the password that it's encrypted with than just to bruteforce the AES encrypted file to find out the password?