I find the 135mm f/2 more useful. It is so fast (in more ways than just the aperture) and much more well balanced.
And I would recommend for the time being the Sigma 85mm 1.4 over the Canon 1.2.
Since a new 135mm might be coming out, I would buy the Sigma 85mm 1.4 if I were you. The Sigma 85mm 1.4 is practically the best achievement of Sigma.
You will not regret it. And if later on you were to buy the Canon 1.2 and use the Sigma 1.4 and Canon 1.2 side by side, I am sure that you will prefer the Sigma 1.4. The only downside to the Sigma is it doesn't have the fancy candy cane look.
5DIII, 5DII, 7D x5, 6D, T2i, T3, 1D X, 10-22mm, 16-35mm II, 18-55mm II, 18-135mm IS x2, 70-200mm f/2.8L II, 24mm f/1.4L II, 50mm f/1.4, 50mm 1/1.8 II x2, 85mm f/1.8 x2, 100mm f/2 x2, 135mm f/2L x2, 200mm f/2.8L II x2, 1.4X III, 2.0X II, 60mm f/2.8 Macro, etc. only had room to list a few Canon items