The "personhood" argument is self-defeating, if you strip it to its essence.
If the argument is simply: "rights accrue to persons and the unborn are not persons" then it is not an argument, it is so-called begging the question: a restatement of the premise that needs defending in a way that looks like a rpoof of the premise.
If you attempt to analyze the argument and inspect what is there in the word "person" that an embryo lacks, you discover that it is personality. Indeed, an unborn cannot exhibit any personality traits, -- he cannot be funny, or earnest, or kind, or what have you. Accordingly, we, adults, do not develop attachment to them like we do to more developed babies. Let us concede that, at least for the sake of the further argument.
Each time we link a right to a stage in development, we do so because there is an ability to do something, that was previously lacking. Now that the child has the ability, we can consider whether it is also a right. For example, children are not mentally or physically able to drive cars, so they cannot possibly have a right to drive a car on a public road. Some adults have no ability to explain calculus, so they have no right to teach college math (even if the college wants to hire them for that purpose). Learn to drive, and you get a right to drive; earn a PhD and you get a right to teach advanced stuff.
Well, what is the ability needed to live? Answer: be a fertilized egg. If an embryo lives, he is old enough to live. If he is a human embryo, killing him is murder.
Seeing the reality...
http://www.cbrinfo.org/
...is also pretty persuasive--- although I must say that though I could watch-- my heart sagging --- the 2 1/2 minutes of "Choice Blues, Chapter 1," I couldn't stand more than a few moment of "Chapter 2."
That was a factor in my prolife conversion, by the way. I was a strongly anti-war high school kid, back in the Vietnam era. Eventually, after a couple of years of firmly and obstinately closing my eyes, I couldn't avoid the similarity between the pictures from My Lai, and abortion.
The logic of "rights" and so forth had seemed to be endlessly debatable, a contest of verbal cleverness. (It's not really, but that's how my debate-cynical adolescent mind had perceived it.) It was the obvious suffering and torment of the mangled bodies that moved me to take it beyond verbal volleying and realize the bloody horror of it all.