It all depends on what you are looking for in a PV.
The Bolt is a basic unit that starts with the battery's max charged voltage and voltage gradually decreases with use which will alter the flavor and
throat hit over the life of the battery charge.
The Gripper has adjustable voltage (from 3.0V to 6.0V) and it will produce the set voltage until the battery is at it's lowest safe voltage,, this will give you consistant flavor &
throat hit
thruout the life of the battery charge. The Gripper also can read the OHM's of the cartomizer/atomizer/clearomizer that you put on it, also you are able to see the level of voltage remaining in the battery.