Can anyone suggest which option is the best and at what times?

mix of both... best is always in the morning

Growth per one section of the body is limited by DNA and the other sections around it. Just like it is normal that the head don't grow so big that the body cannot support it.

So Train the whole body and if you want six pack abs, you can spend more time on it until abs reach a limit, then have to train all the body to develop together.