For those who do not use the vertical grip in true vertical fashion but instead use it with an angled grip, thumb over bore, angle cradled style or just have small hands then you will find full length vertical grips excessive for use and may get in the way of confined environment or at least packing for transport. The short grip gives you just enough contact zone to hold vertically or a more angled grip without having to go any further then needed. Particularly useful of you are the type to switch back and for between vertical, angle and horizontal grip styles on the go.
The attachment system uses a pair of spring loaded bars to quick-attach to accessory rails; it is rather fiddly to get on but that does make it one of the most solid spring-mount attaching modules on the market. This model does have removable panels on the side for installing a paddle switch (for flash light and lasers) albeit it a very short space for a very short switch.