I really don't understand why this needs to be polarized. If Levitt is going to come out and say the effect of the abortion theory is maybe 1 percent, then what's there to argue? I'm pretty sure the actual analysis has stood up to some pretty intense scrutiny. The 'smart policing' theory is a little more difficult to measure and tenuous, but I don't see the problem. It's plausible, at the least, and it's not like these answers are exclusive of one another.
Also, I'm surprised no one has followed up with the lead argument, which might have had a bigger impact on crime than either of the two we've been sitting here arguing about.
here's a pdf
here's an article