I don't think any undecided audience will be convinced by this "mass of cells"-style argument either. But to someone who DOES worry that it is a 'person' being aborted, hearing someone else dismiss that life makes it seem like the pro-choice people are callous and uncaring.
If you're arguing for an audience, all the more reason to be explicit and clear about the underlying ethical conviction rather than just a subjective opinion about what is and isn't life. How this is about a person's right to make the right choice for themselves, privately.
Either that or talk about the pain and hardship brought on by pregnancy, especially pregnancy caused by violence, and the benefit the abortion can provide. That can also be pretty compelling.