If you want t to focus faster, use a 1d (higher battery voltage), but 5d3 is damn accurate. I have he 85 for weddings and it suits my style, even use it in servo sometimes
. However, i also use the 70-200 for more flexibility and speed. Canon 85 is slower than sigma, but sigma can be a pain in the ass: tested it and damn thing would hunt forever where the canon was spot on. Also liked sharpness, mid contrast and 1.2 better
. Let there be no mistake; sigma is much more affordable and has much faster af motor, but in every other aspect, canon wins.