I am quite surprised with 19 Mile brook, it was on state land and had no ammenities yet it was such a popular spot that the WMNF kept the fee area in place as it had high turnover. I will have to check it out as for the last few winters the fee was not collected during the witner then reinstated in the spring. There is or was an attempt to cluster 19MBT with Great Gulf, similiar to some of the parking lots on the Kanc (Champney Falls is a fee area yet the facilties are located at another spot).
With respect to patrolling 19MB trailhead, at best the only patroling is drive bys by state and local law enforcement. I expect Great Gulf has far fewer visits and in general is more break in prone due to its seclusion although 19MB is better for smash and grab as on a quiet night its easy to hear cars coming. Realistically if someone is making a "career" out of break ins like seems to happen every few years, the only way they get caught is a lot of surveilance or good luck like the the stolen Iphone with a tracking ap leading the police to the perps house.