Canon Lenses Vs Sigma Lenses

Sigma vs Canon lens, what is the difference?

Canon EF 70-200mm f2.8 L USM Sigma APO 70-200mm F2.8 II EX DG HSM can someone tell me the differences between these two objectives? Besides the price difference. I've never accomplished anything, but I do not know Canon Sigma. The quality of them? Do I same amount of time concentrating? Etc. Thanks!

I have used both Canon and Sigma lenses and we must recognize that the gun has a better idea. Sigma zoom lens, which had a lot of use, and produces excellent results in the close and began to slide. I guess you get what you pay!

A Canon Lens on the Sigma SD14