Until last month I would have said get the 135mm L
I own the 135mm and it is a pleasure to use it
I owned the 85mm 1.8 and marceled at it's Beauty but with the 135L in the pocket I hardly ever used it.
I own the Mark I Version of the 85mm 1.2 L I use it for portaits (but only for People who wont move fast because the AF is that slow
Recently I shot a series of Pictures at a Beijing Opera Show. Depending on which Scene I used the 70-200 2.8 IS L, The EF 135mm L and the Sigma 30mm 1.4 EX DC. Light changed between the different parts of the opera but usualy stayed for 10 minutes or more the same and I frequently changed lenses always being forced to use high ISOs. Using NIK DFine 2 in Lightroom I was wondering if my NIK Software had issues because every third Picture or so the noise reduction would not improve the Picture at all, the processed Image looking simmilar to the non processed Image. Surprised me a lot until I found that all those Pictures were taken with the 135L. Can#t tell if it is quality of the glass the gain of an Fstop ligt or whatever but with the 135mm I can catch on KungFu fighter flying through the air in a dim lit theatre and the picture looks like prime choice stock material.
So with my favourite clear why not recommending it? Because Sigma is out there trying to shake the market and we are on a rumor page. If that Sigma 135mm 1.8 OS is really coming than either get this one or happily buy a used EF 135 L once their resale value surrenders in front of the Sigma Price.
(and please forgive the spelling mistakes, tonight I have the german spellchecker on and half of what I type morphes into something I have not intended)