SRAM Force. In choosing the groupset for my upcoming Hampsten Strada Bianca, I initially thought Centaur, because I could get it in silver. But I wanted something in the Chorus/Ultegra/Force upper echelon groupset realm. Then I got over the silver thing, and thought I'd go with Ultegra. But I remembered how much I disliked the Shimano shifting method. Then I got to talking more about it with Steve (Hampsten) and others, and they all said, one way or another "Go with SRAM Force, you'll be glad you did."
Part of the decision also rested on the fact that I have never used SRAM products, and wanted to give them a shot. I'm looking forward to it.