I don't own a Rope Wrench or Zig-Zag but I have used the Rope Wrench.
The rope wrench can be finicky as to what rope it works on, the Hitch Hiker seems to be more universal and able to work on a large rage of ropes without a lot of fussing or worry. I also like that the Hitch Hiker is a meld of hardware and software. One drawback to the Hitch Hiker is that it's very heavy but that's symptom of it's "bulletproofness". The new version is a little lighter and smaller then the original one I have.
The main drawback to the Zig-Zag is that you can't use it in SRT applications. Otherwise it looks like a great piece of kit.