Getting a wide zoom lens and saw a couple of them for sale in BnS. My Budget is $1k, I have never use both of these lens before, currently still using kit lens. The Sigma is half the price of the Canon, any diff in them of pic quality? I have read a few reviews on both lenses and was surprised that the Sigma 17-70 was given quite high grading. I am now leaning towards the Sigma. Any opinions? Will like to heard. Thank you.