Canon 17-55mm or Sigma 17-50mm?

Hey! I'm doing music videos and I'm super interested in both these lenses. Realistcally, the money isn't to much of a problem since the Canon is only £100 more than the Sigma so putting an extra £100 wouldn't be a problem. But is the Canon camera a better lens? What are the pro's and cons of having either lens?

Is the best option the Canon? Or does the Sigma have something the Canon doesn't which be healthy for what I want the lens for? thanks!

The Canon has full time manual autofocus, meaning you can override the focus at any point without having to flip a switch, the Sigma does not.

ive had the pleasure of using the sigma, the canon, and the tamron lenses with this focal length... if you can afford it, go for the canon. i would rank them as canon, sigma, then tammy, in decreasing order of quality.
some may say that canon is not worth the premium over sigma, but as you say, its a 100 quid diff, which is not HUGE , and the quality and focus responsiveness and sharpness of the 17-55 is felt.