NOPE - I assure you it will not stay in your bag .
I love my 70-200 for the reach it gives me during the ceremony, and if I could only afford one, it would have to be the 70-200IS because of the utility.
Having said that, I LOVE the 85 f1.2. When I am shooting portraits it is practically glued to one of my bodies. I find that the critical focus accuracy of the 85 is better than my 70-200 at 85mm. It is slow to focus, making it difficult for moving subjects, but Canon has no equal among portrait lenses. Since my business is built on the portraits I create more than my candid work, I would have a hard time getting rid of the 85. In fact, for an engagement or family portrait session, I usually only bring the 35 and the 85.
I did a shoot last year for a local TV network where I had roughly 2 minutes with each member of the Boston Celtics. Because the hot light setup was a little tight, I used the 70-200 instead of the 85. I got a TON of slightly OOF images with the 70-200. At one point I switched to the 85 and everything was spot on. I've done micro adjust with both lenses, and my technique is the same, but the 70-200 couldn't deliver.
Conversely, on the dance floor at a wedding reception, the 85 struggles a lot. I only really use it during the first dance, where they are moving slowly and AFTER I have captured a bunch of "safe shots" with room lights and the 24-105. When I do nail it, though, it is pure magic!
I had a really good copy of the 85 f1.8 before I came across a cracking deal on the f1.2 ($800
). The f1.8 got left in my bag a lot once I bought the 70-200. The f1.2, once I mastered the learning curve of the extremely thin DOF wide open, does not!
So I guess the short answer is: If you want utility, the 70-200 is better, if you want magical portraits, the 85 f1.2 is your huckleberry!
Most of the images here are with the 85 f1.2: http://jamisonwexler.com …m/blog/category/weddings/