I don't have a cannon so I can't answer that... But... I do have fixed focus lenses (105mm, 35mm, and 30mm) as well as zoom (14 - 54mm, 45 - 150mm, 55 - 200mm, 150 - 300mm and even a 600 - 1300mm).
As for quality - I can't recall the exact name of the term where you lose some part of your photograph's edges because of zoom... But it is apparent and in some cases requires cropping to accommodate... although I rarely crop.
I find zoom macro and using a fixed focus macro to be comparable at low res, but at high res I'd only use fixed focal.
eg:
Fixed focus (105mm) macro:
Zoom @ 300mm (essentially macro):
Zoom @ 300mm (long distance):
Zoom @ 1300mm (hand held, long distance):
Now which one(s) have been cropped? Bet you can't guess...