[daft_biker]

Originally Posted by LoveDSLR

BTW, One of the UK's leading flower and garden photographers, Clive Nichols uses his favorite Canon 180mm for his works. He likes to have the full control of the DOF to make the flowers pop out. (Source: PhotoPlus May 2008 edition).

I suspect the longer lens is used for other reasons than DoF control - the 180mm goes from f/3.5 to f/32 where the shorter lenses typically go from f/2.8 to f/32.

An 80mm focal length difference in telephoto lenses doesn't really make any odds to DoF for macro - not unless you have low standards and calculate DoF for a small print from a large sensor. High resolution DSLRs require a very small CoC to be used in DoF calculations if you want them to hold up to close inspection.

I would expect the usual reasons for using a long macro lens apply - narrower angle of view so it's easier to get distraction free backgrounds, more aperture blades for creamier bokeh and in the case of flower photography the increased working distance gives you more space to light the shot and you're less likely to cast a shadow. For insect photography longer lenses also help you keep your distance so you are less likely to spook the subject.

I'd suggest the narrow angle of view and creamy background makes subjects stand out.

Generally speaking most folk buy the longest macro lens they can afford for that kind of shot.