Yep, that's basically it.
Autococker operates exactly like a pump, but with a low pressure re-cocking mechanism (consisting of a regulator, 4 way valve (or solenoid valve in an electro) and a pneumatic ram) attached to the front in place of a pump handle. In a mechanical cocker, your trigger serves two purposes. First, it trips the sear, releasing the hammer and firing the marker (this would be the "beginning" of the "firing cycle"). It is also attached via a linkage rod to the 4 way valve, which moves back and forth with the trigger and directs low pressure air from the regulator to either the front or back of the ram to make the bolt and attached back block move backward or forward, cocking and recocking the marker (this being the "end" of the firing cycle). In an electronic autococker, the same thing happens, but instead of being attached to the 4 way valve via a linkage rod, the trigger is actuates a switch on a circuit board and sends a signal to an electronic solenoid valve in place of the mechanical 4 way valve.
The Impulse is a typical open bolt electro. When you pull the trigger, you actuate a switch on the circuit board, sending a signal to a low pressure solenoid valve to direct air to an internal ram (much like the autococker, except the ram is internal and has the hammer attached, and the bolt linked to it via the hammer). The ram, and subsequently the hammer, moves forward, carrying the bolt with it. The hammer strikes the valve releasing air into the bolt chamber and a ball is propelled forward. Then, the solenoid valve resets, the ram moves back, bringing the hammer and bolt with it, and resets the cycle.
Impulse = more dummy proof, IMO. But it depends on your preference, and your ability and willingness to learn about the marker you choose (with the impulse, you'll basically just have to learn how to turn it on. With the cocker, you SHOULD have a pretty good idea about how the re-cocking system works and timing and troubleshooting.) To give a way overused answer, Try 'em both and see which one's "right for you". Good luck.