The sigma seems to have a lot more edge CA. Can you see it?
It's not CA. CA is when there are in-focus items at the edge with a fringe showing, and that's not what you see here (or what I've seen from the lens in general.) In out of focus areas you'll see some color fringe, which isn't CA but I can't remember what it's called - spherical aberration?... still, very common, you'll see it with almost every fast lens at the edges of closest focus in the heavily OOF areas. Someone else with more optics background than I have corrected me once on the topic...