I believe, when speaking about Abortion, we are less speaking about abortion or anti-abortion as we are the ideas of regulating morality.
What value do we put on people's ability to make their own choices for themselves, and how far will we go to control them?
Yes, there is the moral issue of whether abortion is murder or not. I think this pales in comparision to the issue of legislation though.
An abortion will be performed, whether it is legal or not, if the mother truly feels that she is justified or right in doing so. The personal morality has already been set.
In fact, in the United States, the same amount of abortions were performed before Roe vs Wade as for years after, annually. The increase in abortions, I believe, is do to more factors than just the legal status of abortion.
Back to the point though, are willing to make our own morality the morality of everyone else through legislative processes? Are you willing to have someone tell you what's right for you and what's wrong just because they had a personal conviction that it was wrong?
Abortion is more than free choice, it's about rights. What right do you have to determine what is best for you? What right do you have as a citizen of your country?
I personally, am anti-abortion (I refrain from pro-choice and pro-life for they are jargainistic terms that are meant to compele emotion). But, I'm not willing to let a law decide whether I should be or not.