What to choose: to be a novel writer or a university lecturer(proffessor) both in a medium level.?

I'm a 25 year old Australian and I can relate to this question as I'm hoping to be an author eventually too. In this situation I'd go for the Phd first and become a university lecturer/professor and finish my novel after I was settled. There are very few authors that can actually make a living out of writing. Most have to have some form of job to add to their income. Even some of the quite well known ones still have a day job. And I know that teaching in schools or universities is actually quite a popular day job for writers as it ties in with their art and they can work their work so it doesn't completely take over their lives.