9 day trip - North or South Vietnam in early August?

Hi all,

My girlfriend and I are planning a 9-day trip to Vietnam in early August. We will definitely be spending time in central Vietnam, but are unsure whether to spend the rest of the trip in the north or the south.

We are leaning towards the north but it sounds like the weather may be better in the south. There is so much to do around the whole country that making a decision is very difficult!