C'mon! Almost 100 views for this question and only 1 reply?! Surely, someone must have some experiences with these lenses.
Er maybe not -- some of us were cheap and bought the Canon 35mm f/2 before the Sigma 30mm f/1.4 was announced.
Things I like about the 35mm f/2 (although you didn't ask): it's small, light, and inexpensive compared to the 35mm f/1.4. For sharpness photographing small children in low indoor light, I expect the limits are my handholding technique and the ever present subject motion.
The thing I don't like about the 35mm f/2 is the buzzy autofocus. In practice though subject noise helps to cover this up too, when the the subjects are small children in motion indoors.