Travel lens dilemma: help me decide

[earthbound]

Hi everyone,

I'm going on a 2-week Japan trip soon and I will be bringing my camera with me (of course). I currently have a T2i, 18-55mm, 50mm 1.8, and 85mm 1.8. I have money for one more lens, and what better timing to buy than now so I can bring it for my trip.

Right now I'm torn between these 3 lenses:

• Canon 10-22mm
• Canon 15-85mm
• Sigma 17-50mm OS 2.8

I tend to shoot more on the wide end hence my choices above. They're all very different, with the 10-22mm giving me the wide angle, 15-85 a wider and longer range than my kit lens, and the 17-50mm the fast constant aperture.

I was hoping that I can get opinions from you guys, especially if you've done a lot of travel photography. What ends up being the most important to you - the extreme wide angle, the flexible range, or the speed of the lens?

Image quality is also very important to me. Which of these three lenses will give me the best IQ or are they pretty comparable?

Thanks in advance.