Looks like the smaller coil on the AT Gold has some advantages due to it's smaller size. Check it out:
http://www.youtube.com/user/GarrettDetectors#p/u/1/1rB5Ke3SVdM
http://www.youtube.com/user/GarrettDetectors#p/u/2/dZ5G0owt5M8
http://www.youtube.com/user/GarrettDetectors#p/u/1/1rB5Ke3SVdM
http://www.youtube.com/user/GarrettDetectors#p/u/2/dZ5G0owt5M8