Conclusion: Only the 180s for shy crawlers, for static objects (flowers, etc.) both for portraits and "normal" pictures the 100er.
Who does not specifically small cattle stuff is probably better off with the scans more universal 100.
In More Detail:
Speak the large working distance, the class processing and last but not least the excellent optical quality in the macro area of the EF 180mm L. However, it is significantly larger and heavier than the EF 100 L and requires 72mm filter. The nonexistent dust has not been lacking in the practice itself in the swamp and jungle (I change the field never Bodies, therefore absolutely dust-free sensors).
The EF 100mm L has the smaller working distance & diameter, is lighter, has a very good finish and also a very good optical quality. Also 67mm filter diameter are slightly cheaper. The lower price of this lens is hidden that the tripod collar D is absent (Canon 135), which brings the 180's. The optional lens hood can at 180, thanks to the larger open space, even at 1: 1 is used and tolerate it if one so supports the 1.1 kg cars on the ground. To the tripod receptacle the EOS EF can be worn 180 Kombi comfortable.
But the key difference is the longer focal length of the 180: the object is fantastically set off from the background, also has less background in the image, making the composition a little easier. For the longer focal length shrinks the object a little stronger, it seems minimal flat & slightly less plastic. This effect is quite subtle, the crop already apparent. Since the F2.8 to F3.5 does not matter (1: 1), the depth of field in both cases is too low and even at F8 extremely thin. Striking is the difference in close range from 1: 3-1: 10, here is the 180 is still a very narrow focus, the 100 puts to something faster. Generally, the sharpness is at 1: 1 super, Fade change the fact virtually nothing, often is anyway worked at F8, to ever have a usable focus range (or even merciless Stacking).
In the handling of the larger working distance curse and a blessing at the same time:
A blessing because small crawlers often the presence of the photographer did not even notice, and if they do, at least not flee but remain seated quietly in the hope of being themselves not yet discovered.
A curse, because with larger objects (1: 5) already 0.9m between lens and object, protrude into the fast grass etc.. Here is such a lot of freedom sometimes easy to keep hard free / receive or can the work be too small (1.2m plus kneeling photographer). The relatively high weight (1.090 g to 645 g without clip) may in the long run tire the hand, which is acknowledged with trembling. But it is precisely at 1: 1 inertia helps to keep the camera steady. Of course, a tripod or bean bag is the better option, but completely ruled out in animals like jumping spiders.
For photographs of flowers and other objects sedentary work I like to use a macro with 100mm or 50mm (Canon or Zeiss now). Here, the distance does not matter and I always use a tripod. AF and IS are me because no matter still. Is also 1: 1 virtually not required 1: 2 except for some absolutely tiny Orchideenblütchen. In the shorter focal lengths to me the hint more of plasticity like better, the bring this.
In "normal" use, the 180 is a supremely good telephoto, the AF is (limited to switch to> 1.5 m) from 2-10m even quite fast. For distant objects (about 35 m) can occur at edges bright light fringing (depth effect). In the macro never occur. Also, the macro focus from 5m is running extremely short, it may be focused only quite inaccurate (180 ° for 0,48-1,2m to 35 ° for 1.2-INFNTY.). The entire optical system is precisely designed for short-range, not as Tele on large expanses. Both set to F4 easy to focus on, then they are very sharp and - equally important - very contrasty. The sharpness of the contrast seems subjectively at 180 minimally better, possibly on 100. But the differences are in the homeopathic area.
The EF 100 L with AF and IS a very good all-round flexible lens that can be used very well for portraits, etc. (and often is). Here AF and IS played their strength and also clearly justified. In this respect, the limited mounting the EF 180 L without IS and its clearer telephoto focal length, the specific objective and the 100.
Apart from that we were doing something wrong with either of them.