I have the three piece (sizes) set from Blue Point. I ended up getting them over the Knipex (one size only) when I found the Knipex were too big to grip for what I used them on most.
I looked the Harbor Freight and passed. The rounded tips were not well aligned , burned looking metal, etc. The Blue Point are but much better in that regard.
Wouldn't mind getting some of the Snap On pistol grip style too.
I also figured the three sizes might lend themselves for other uses such as pulling/ plugging RCA plugs in the back of hard to reach into stereo cabinets, manipulating other round stuff. Just seem like something that might come in handy for other than spark plugs.
Seth