I found that dirt followed by wear caused the King grip to lose some bite and release the pipe. We only used one.
The Maxi Grip wears well because the lead end is insdie the bullet. Also you can be flexible with pipe size like .75 to 1.25 inch pvc in one and 1.5" to 2" in another. Putting wire in with it is not a problem. Kind of expensive to play with this stuff but consider it at replacement time.