Canon 28-135 or Sigma 24-70

Thanks everyone for those helpful advise.

I think I'd go with the Sigma 24-70. I've tried the Sigma 18-50 but it feels to wide for me. The review at http://www.pbase.com/f​stopjojo/2470v28135 did help a lot. thanks Mr. Jojo.

Off to the store now.

Thanks.

Something to ask about Sigma 24-70. The focusing ring is a clutch to switch between auto and manual focusing. Is there a small button at the botton for AF/MF? If yes, do I need to switch 2 switches to convert to MF?

I know Sigma is near in image quality to Canon 24-70 except blurred corners at 24mm. Since Canon's price is nearly 4x of Sigma, is it worthy to buy Canon 24-70 for its quicker (how much?) AF, silent focusing (is Sigma really noisy?), and full time manual focusing?

I think Sigma can refer to Canon's hood design. It's a clever design to hide the protruding front glass.

still thinking of selling that 200 2.8L?