You're right; the ending of abortion is "not that important", it is critical to the fabric of the United States. Abortion must end, and hopefully Scott Brown is fully-on the pro-life/anti-abortion team. There is no such thing as being ok with a woman "choosing" to kill the innocent unborn, and there is no possible way to defend or justify such an action.
I am personally pro-life, but there are many issues much more important in this election. Scott Brown will be a consistent vote on the majority of conservative issues. RvW will only be overturned by the SCOTUS, not congress. Scott will vote to confirm conservative judges, that’s where he can help the most with RvW.