Yes, I have had both. I started with the Sigma 30/1.4 on my 7D.
It was appallingly bad in the corners. Like 10 pixels of CA/smear.
I said to myself, "I've just paid £1200 (camera) + £400 (IIRC) for this lens, and the overall image quality is worse than a £300 P&S camera's.". There is more to it than that, of course, but no, the lens was quickly returned and I got the Canon 50/1.4.
While the Canon 50/1.4 does suffer from quite bad "halation" (light smear, loss of contrast, etc.) wide-open, once stopped down to f/2 or so, it is very sharp, but you still have the f/1.4 option when you need it.
My experience with the (admittedly one sample of) Sigma lens was so bad, that I doubt I'll buy another Sigma lens ever again.