ssl_cipher_list

Is there a difference between not setting #ssl_cipher_list = or setting to nothing ssl_cipher_list = or setting to ssl_cipher_list = PROFILE=SYSTEM

Which is the best preferred way for default?

Also, the docs say "You should usually prefer server ciphers and their order, so setting ssl_prefer_server_ciphers=yes is recommended." however this setting is =no by default. Why? Should it be yes or not?