The Stingray is legally grayer. Carrier data is squarely within the third party doctrine.[1] The fourth amendment protects individuals' rights in "their persons, houses, papers, and effects." A carrier's billing records are not your papers and effects; they're the carrier's property, generated by the carrier for the carrier's own internal purposes.[1]

The Stingray, however, interacts directly with the suspect's cell phone. Third party doctrine becomes irrelevant at that point, and the government has to fall back to arguing that whatever a Stingray does is not a "search" or a "seizure."

[1] Doesn't mean the Supreme Court won't limit third party doctrine in this case.

[2] Say some nosy neighbor keeps a list every person that enters or leaves a house in a neighborhood. The resident of the house is murdered. The nosy neighbor's list shows that you entered the house the day of the murder. You can't assert a 4th amendment right as to the nosy neighbor's list. It's a paper that's about you, but it's not your paper.

The cost to deploy a Stingray is still significantly higher, which may be a factor.