Able to adapt the rig quicker for different situations and angles without having to change parts. The only limits is there are attachment point and unable to put it on a tripod, however its not a huge issue as most use a quick release system to get the camera of the rig. But also the great thing its a really small package you and dismantle it or fold up so it can easily fit into a small bag and not take up a huge space.
The price making a gunstock rig varies from the simplest of $15 to the more advanced $47 USD. So I have listed the different variations you can make, that suits your budget and style. The list contains the price, object and links to Ebay with the correct search terms to directly find what you need.
The Simple is the lowest costing version using a Cold shoe stand for external flash as the gunstock however it does give you the support, for me I feel this limits you a little when doing pan or tilt movements .
For me I like the Basic as you can setup it quickly and use it as a gunstock and looks less intimidating than most rig and easily walk around without people noticing it too much.
The Plus ads a handle as the reason is that most DSLR has a tendency to heat up especially adding body heat from your hands on the camera grip can increase and make your camera heat up faster. To avoid this its better to have your hands off the camera plus being further away from the camera limits the shakes even more.
$14 – 11inch articulating arm
2x $6 – Sponge handle grip
$10 – 323 Quick Release
$7 – C Bracket
$4 – Mini Ballhead
The advances adds a bullhead on top of the grip, to improve the handling and able to hold the rig in the most comfortable and ergonomic way. Angling the handle would lessen the strain on your hands and able to hold the camera much better and able to lessen the shakes even more.
If you want more info about the Cage follow the link below: