I just ran across this and clicked through to the discussion; sorry for being a year out of date, but I hope you don't mind the comment anyway!
I enjoyed reading the piece but I felt like it was missing any reference to what (to me) is the most germane point in the abortion debate: any reference to the person who wants the abortion. To my mind, the personhood or lack thereof of the foetus really doesn't matter very much, because it's growing in a person whose personhood is indisputable and who doesn't want it to be doing that. I think the piece would be much improved if the Apologist made something of the point that even if the "personhood" bullet is bitten, the Contrarian is still left forcing someone to provide physical life support for another person against their will.
To my mind, the personhood or lack thereof of the foetus really doesn't matter very much, because it's growing in a person whose personhood is indisputable and who doesn't want it to be doing that.
In many situations, we are happy to make one person suffer or die - even if they don't want to - for the good of others. Child support, taxes, any form of imprisonment or execution or corporal punishment, the draft... And as well, those are all cases where the probability of saving a life are all vastly lower than in abortion where you know for certain that the fetus will die.
A few years ago, I wrote a little dialogue I imagined between 2 materialists, one of whom was for and one against abortion, centering on the personal identity question. I recently cleaned it up and added a number of references for the biological claims.
You can read it at An Abortion Dialogue.
Early feedback from #lesswrong is that it's a 'nicely enjoyable read' and 'quite good'. I hope everyone likes it, even if it doesn't exactly break new philosophical ground.