I bought this:
Counting from the handle end, the second one simply slices through the whole cable and is very sharp and effective.
The third one is adjustable, and takes off the outer sheath after adjusting the thumbscrew above it.
I'm at a loss as to what the 1st and 4th ones do. I tried them, the first makes two little notches in the side of the cable, can't think what that's for. The 4th, depending which way up the black part is, strips to 1mm or to 5mm.