The 135/2 is a *superb* lens for low-light work, and unlike a macro lens, it is designed with an adequately long focusing throw to actually NAIL focus in the 75 to 4 foot range in autofocus mode, shot after shot--that is something most macro lenses can not do nearly as well as a field telephoto. The 135/2 is also a slight bit lower in contrast than most modern macro lenses, so it renders human skin tones in a nice,pleasing manner, plus it has defocus control, which can throw the background somewhat more out of focus at wide apertures, OR which can be used as an in-camera soft focus lens. it works pretty well in manual focusing, mode too. In terms of its T-stop, or actual transmission, my 135/2 AF (a pre-D model) is the 'fastest' lens I own.
The 135/2 is a pretty good lens for lower-light action shooting, like nightime football and things like that. The 1235/2 is very,very hand-holdable, unlike the 200/2 which is a monster after more than about five minutes, and really is a monopod or tripod-only lens for any length of time. 1,000 Euros is not exactly small change, but the lens design is very,very robust; I got my lens used and it had been carried and used *exceptionally* hard and for many seasons, with the entire crinkle finish worn off to smooth on one side of the lens hood, so the lens design itself is very sturdy,and it should be a "lifetime" lens in normal use.
The 105 DC and 135 DC have a cooler white balance than more-modern lenses,and a much cooler,more neutral rendition of color than any Sigma I have ever owned. If you can spare 1,000 Euros you will be buying a very nice 135mm f/2 lens. It's not a decision to make lightly though.