I'm, personally, pro-life because with so many people who are unable to have kids, I feel that those who are lucky enough to be able to conceive should cherish it.
Why I would vote pro-choice - aborting a fetus before 25 weeks (I think it's 25 - whenever their lungs develop fully) is not murder. Murder is when you take the life of a live person, NOT a thing in a woman's body that can't live on it's own. After 25 weeks, if a fetus can live without the mother, than it's a person and because of the third-trimester, we don't have to worry about that.
I would also vote pro-choice before I voted pro-life (if I was to vote on this issue alone, though it isn't on my priority list for picking a candidate right now) as it would have to be a candidate who understood that being pro-life ISN'T just about being pro-birth/conception - you need to be as close to sure as you can that that kid isn't going to starve, is going to be able to get an education, and is going to get the healthcare they need.
You can't be pro-life if you don't support and protect the ability and opportunity for that kid to live a decent life.