You could just measure your shoulder width and see what's closest. Personally, I prefer a 42 for the tighter feel even though when measured I've been told I need a 44. The 44 seems too wide, funny how only 2cm can do that.

The other thing to watch for in the bars is the reach - I had to swap from a Ritchey Carbon Logic to a Carbon Streem because the Logic was just too long a reach for me with the 110 mm stem. In the end, I also replaced the 110 with a 100. Yes, I was measured and fit before the bike was ordered - just shows you how personal preference after a few hundred miles goes a long way.