I am on the tail end of an assignment in Japan, and I have seen the arcades and such quite a bit with these crane game style prize machines. The machines with the 3-fingered metal claws (and controlled with a 2-axis joystick) seem to give you at least a halfway decent chance at getting something. I have avoided using the ones with the large crane and the 2-fingered claw as in this picture (of which the Sega "UFO Catcher" machines are probably the most common) because those seem to be calibrated so that the fingers generate almost no torque. Many times I watched other people using them, and even when they maneuver the claw to exactly where it should move the prize the most, the object barely gets nudged. The claw can barely pick up anything either; even if the fingers close around the prize when the claw assembly is lowered, the weight of the prize forces the fingers open when the claw assembly moves up again so the prize is merely shifted around slightly.

The 3-fingered metal claws are actually able to pick things up reliably, but the tricky part is that when the claw assembly hits the upper stop when rising, it often jostles the claw such that things can fall out of its grip when the fingers move from the impact. There was one time when I was able to get a small plushie from one of those machines in 1 try, as it seemed to be near the optimal size for the claw to pick it up!