The main reason for the air force switch is payload capacity. The Predator can only carry 204 kg (450 pounds) internally and 136 kg (300 pounds) externally, compared to 364 kg (800 pounds) internally and 1.36 tons (3,000 pounds) externally for the Reaper. The Reaper can also fly faster (cruise speed of 300 kilometers an hour, versus 160 for the Reaper). Max takeoff weight for the Predator is one ton, compared to 4.7 tons for the Reaper. Since first flight in 1994, Predators have spent nearly a million hours in the air. So far, nearly 500 Predators have been built, most of them for the U.S. Air Force or the CIA. Each Predator costs about $5 million (without sensors, which double the price).
Predators will continue to be used by the U.S. Air Force until accidents and enemy fire take them all out of service. Meanwhile, Predators will be built for a few more years, to take care of foreign military orders. A slightly larger Predator, the MQ-1C Grey Eagle, is being built for the U.S. Army (which wants more than 500 of them). The manufacturer (General Atomics) is trying to extend production of the basic Predator, to supply civilian demand for the RQ-1 Predator XP. This is a demilitarized MQ-1, modified so that it's difficult to arm. Because of that the U.S. government certified the RQ-1 Predator XP as a civilian aircraft and eligible for sale to anyone.
The big attraction of the XP is its track record. Over its nearly two decades' service, the Predator has established a reliability record approaching that for manned aircraft of similar size (single engine commercial airplanes). The Predator had an average availability (for use) rate of 90 percent. The XP version can be equipped with air or ground search radar, in addition to the usual day/night camera. The XP is also inexpensive, costing about $5 million with minimal sensors (day/night video camera). That might be adequate for border/maritime patrol and other police work but the XP can also be equipped for resource management (checking crops, surveying forests for lumbering, or searching for minerals). Satellites are used for a lot of this resource management work, but in many situations an XP can do it cheaper, even with the more expensive sensors required for this kind of work. The XP can stay in the air for up to 24 hours and operate as high as 7,620 meters (25,000 feet).
The XP still has a problem with flying in areas where it is likely to encounter manned aircraft and local laws prohibit or limit UAV use. But this is changing, especially as navigation sensors on UAVs become more effective. So in a decade or less, suitably equipped UAVs will be legal in airspace full of manned aircraft.