This was the cheapest Wire Saw on Amazon that I could find.
It does what you want it to, no reason not to get this one from all the others.
I just can't compare it to the others because I don't own them, but I can say that if you're tight on money and need a wire saw, buy this one. It does what they all do.
Although cutting through thick pieces of wood/tree is obviously going to take a while. It cuts through thick plastic even easier than wood as the heat melts the plastic. It doesn't cut through metal though.
A good thing about this wire saw (like I said I have no idea about the others) Is that it can't blunt because it's strands of metal wrapped around each other so there are no teeth. It also means it's safer to hold the wire, but it will leave marks or snag on your skin.
4 Stars because I couldn't tell you if there's a better one. Just that this one is good enough anyway.