Set 3 - at 200mm
Canon 70-200 f4 -at 200mm 1/400 f4 iso100
Sigma 70-200 2.8 EX DG Macro II - at 200mm 1/400 f4 iso100
Again, the sigma produces a brighter but warmer toned picture. But at maximum zoom of 200mm, the focusing and sharpness are still very good at f4. I think the canon bokeh is better but that's a matter of taste. The canon is also sharper, but the sigma's sharpness is not bad at all.
And for comparison, used the sigma at f2.8
Sigma 70-200 2.8 EX DG Macro II - at 200mm 1/400 f2.8 iso100 (but I forgot to increase shutter speed, so this is at the same shutter speed as the 200mm f4 shots, so its much brighter)
Again, much better bokeh at f2.8. Due to the thin depth of field of the f2.8, sharpness is good only around the focus point (the blue star), but I still find it pretty sharp considering its shot wide open at 200mm