the macro isnt great on the big lens so im wondering what would the best purchase be for my nikon lens, extension tubes or macro filters as per link below:
http://i9.ebayimg.com/01/i/05/1f/74/8e_1_b.JPG
i took this dead fly pic with a nikon 18-55 with a +10 macro filter on the front of the lens.

incedently, what does +2 +4 +6 +10 mean for macro filters?
i have tried these screw on filters before with my other lenses, the 18-55 worked fine, but the 70-300 went really hazy with one on.
so to summarise, wha does the +10 bit mean and whats better, tubes or filters?