Both have their advantages and disadvantages. If you are training multiple dogs, wingers extend your training day significantly, since you have to walk out to each one and reload between dogs. Also, you can't fire a second one for a dog that loses the mark, but you can repeat the sound to pull the dog back into the AOF. I prefer using ducks and wingers for training, but bumper launchers certainly have their advantages. I have and use Gunners-up wingers (4), Bumper Boys (3-8 shooters and 1 two-shooter) and Ramponi box launchers (2).
