This really depends.
Taxes are lower in Germany but Munich has become very expensive to live in, even compared to Oslo. However, Norway includes its health insurance and better pension benefits in its taxes which come on top in Germany.
Oslo is much smaller than Munich, therefore commutes are typically shorter but this depends on where you would live and where your job is located. Work hours are shorter in Norway and tend to be more flexible.
Both countries provide free schools but if your partner wants to work, Norway offers better opportunities, especially with children in kindergarten age as Norway is very layed out for two income families. If your partner is not intending to work, Germany is probably more friendly with its tax system whereas surviving on one income can be very difficult in Norway.
Health care is of high standard in both countries.
I lived in both cities and chose Norway, partly because me and my partner both want to work full time. But either city is a great place to live.