Opinions aplenty, but no experience with these lenses! You’re talking about 0.5 stop between the lenses, so no big deal. Ditto with focal length.
So, what is left?
Price.
Ease of manual focus.
Sharpness at wide apertures.
Bokeh.
A
test of the Canon 28.
Another
test of the Sigma.
Both appear to have weak edge and corner resolution, even compared to zooms; not great considering the tests are on APS. HTH