[A]mple evidence suggests that the Maricopa County policy is costly, imprudent, incapable of stopping illegal immigration or human smuggling rings, and prone to serious official abuses by law enforcement personnel. Despite some successes, its overall costs far outweigh its benefits, a conclusion you'll likely share after taking a closer look at the record over the last half-decade.
Friedersdorf (with the ample support of an old newspaper investigation) makes a convincing argument, but I'd like to nitpick the idea that this is the "best" case. Cost-effectiveness is certainly the easiest case in that it appeals to the widest range of people, and it's certainly important, but the best case in the long run isn't that illegal immigration is an evil we are incapable of stopping, but rather that immigration is a beneficial phenomenon that we should not seek to stop. Under Friedersdorf's logic, if someone more innovative than Arpaio finds a way to scare off illegal immigrants more cheaply and humanely, then we should support it. But that doesn't address the fact that immigrants respond to labor demands rather than a desire to populate the US with foreigners, nor does it acknowledge that the United States enjoys a net benefit for their presence in the country. If immigration advocates can win the argument on that terrain, the victory will likely be more enduring.