No real advantage between the two, but the electric may cause you to have gremlins in the bikes electrical system. Do a quick search and you will see why I went with the vacuum model. I would go with the vacuum because of the space restrictions in the Gen 1, but it is your choice and you may come up with a new idea for the control module placement.
This is by far the best mod I have done to my bike. I ride 120 miles round trip to work when weather permits and it is rock steady on the interstate. It makes the ride so much more comfortable and increased my mileage because there is no variance in the speed up and down hills from my wrist.
You will not regret it and no matter what anyone says, the throttle locks out there cannot even compare with the true cruise control. I had a throttlemiester and it was good, but the CC is much, much better.