The main reason to use the Helicopter/Chod setup over any other is when you need to fish over weed/silt/detritus, the choice of setup depending on the depth the lead will penetrate.
I use the same lead system for my Helicopter rig as I do for my Chod rig with only one difference, how I place my top bead.
Both setups are designed to be efficient and safe using the breakaway method of attaching the lead. In this instance (figure 2) I am using Gardner Dropout Chod Safety Clips either single or doubled up for a harder cast. The beads used are the soft rubber type with a tapered hole, one side being smaller than the other (figure 6). This allows them to grip the double splice for the Helicopter setup (figure 3) yet slide up and off the leader if needed.
Figures 1, 2, 3 and 4 show you my Helicopter setup. I tie a longer splice for this so I can place my top bead up to a depth of around 10 cms (4 inches) from the lead, anything more than this then I switch to a chod rig.
Figures 5, 6 and 7 show you my Chod setup. Here the top bead is held in place using a small length of ESP (drennan) Shrink tube (figure 5). This grips the leader and is lightly inserted into the large hole of the rubber bead just enough to hold the bead in place on the cast, yet still pull up and off the leader if needed (figure 6).
The Safety clip is connected to the leader via a large rig ring (figure 2) and the whole lot covered and secured by a helicopter sleeve (figure 1).
When it comes to the choice of lead I always go for a torpedo lead as they do not snag as easily as other leads and will lift out of chod easily. They also cast further than any other lead so you don't need to cast as hard helping to preserve the safety clip.
As far as the rigs go you can interchange them with either setup and I often use the 10 inch popup rig (figure 4) with the chod setup (figure 7), I use a popup with both these rigs except when it comes to fishing over silt where I might try a bottom bait on the 10 inch rig.
In my experience neither of these setups perform well on a slackline and some tension is needed in the mainline for them to work effectively.