The converter is a very nice thing to have. I don't use it because you add an object (the lens from the converter) to your lens wich can create flare. I always look for the quality of the glass and to prevent any lens flare.
It doesn't matter if you use a macro converter or extension tubes, you are going to loose light and you need to changes the shutter speed op apperture.
I use extension tubes for extreme close-up macro. It is just a tube that mounts between your lens and your camera body. The tubes I use transver all the function from your camera to the lens. You get cheap ones for about R150 (3 in a set) but they can not transver any camera functions to the lens, that means everything is manual.