Y'kno, I went up and googled "Boeing Global Hawk" and it brought up a site that was a literal catalog on state of the art drones and who's using them for what.
The "Predator", the "Reaper", the "Mariner", and a whole host of different names and variants are basically the same airframe. Portability and load are what makes the differences as far as I could see. The Global Hawk works at 65,000 feet of altitude where the Predator (and 90% of it's variants) function from 30,000 to about 55,000 feet. Wingspan varies from 66' to 82' and the powerplants vary depending upon the designed altitude.
The Global Hawk seems to be the most prevalent aircraft within the country's borders, but Homeland Security and DEA is using the Mariner on both borders.
And no Virginia, we can't shoot 'em down. but the Russians (or the Chinese) figured out how to deal with them in the Persian Gulf and Afhanistan. They found the UHF bands they were using to control them over Afghanistan and Pakistan and then figured out the scrambling code, and Voila!, the Iranians have taken over the controls of several and landed them in Iran. They didn't shoot them down, they stole them!
An acquaintence who was in the Air Force and was part of the team at Nellis (Las Vegas) who flew the Drones over both Afghanistan and Pakistan told me that during Bush 43's term, they used the drones sparingly because they knew the Russians were monitoring the control bands, but after the Mocha Messiah took over, the flights increased about 1000%. Then after Iran got the first predator (classified info) the Generals notified the CIA that they needed to cut the overflight frequencies over and around Iran . . They didn't and one of their really secret, state of the Art "Frisbees" got kidnappped . . You read about that one . .
Then The DoD moved the controllers to Kandahar, Afghanistan. That's why the DoD created the "Drone Pilot's Medal" . . now they're "In Country" rather than in North Las Vegas . . Dunno if they're still using the COMSAT or direct control, but it's harder to "Kidnap" a drone when your signal is almost impossible to override . .