Hi Jessica!
Even though I use Nikon cameras and lenses, I'll try to give you a little help as your question would be the same if you replaced the name "Canon" with "Nikon" as the quality of the two products is the same.
Basically, it depends...there are consumer grade Canon lenses as well as pro..there are also Sigma lenses which are aimed more at pros than amateurs, so it's difficult to just compare the two names. One really should be more specific and compare actual lenses if one is to be objective.
That said, in my very personal opinion, both Canon and Nikon produce some very fine lenses, and being as the lense is the one item that will really make a difference in the quality of your images (if we now do not include the photographer him/herself, of course) then I do not believe the lense is the best item to try and save money on...
I would rather use a cheaper camera body (hus) and a good lense, than use an expensive body and a cheap lense..
Sooo, my personal advice (and others will undoubtedly give you other views
) is if in doubt, go for a good Canon lense and you'll surely be happy you did..at very least you shouldn't be disappointed...
There are, indeed, good Sigma lenses, but overall they don't have a reputation to compare to Canon. Bare in mind I am speaking generally about the whole range, though, and not about any specific lense.
Hope this helps abit.
Happy Easter,
Duncan
