The Sigma 35mm f/1.4 Art is a great value when compared to the Sony 35mm f/1.4 because it outperforms the Sony in some ways for around $700 less.
Sigma 35mm f/1.4 Art
Wins eye AF Sharpness
Equal AF speed for photos
initial focus can be giddy at first with Video AF
Sigma best for Photos
Both have AF/MF Switches
Neither have a focus hold button
Both made out of metal
Sigma matt metal
Sony 35mm f/1.4
Equal AF speed for photos
Picks up face farther with Video AF
Smoother transition with Video AF
Sony best for video
Has an aperture ring that can be clicked or unclicked
Both have AF/MF Switches
Neither have a focus hold button
Both made out of metal
Sony shiny metal
Sony 35mm f/1.4: B&H Photo / Amazon / Adorama
Sigma 35mm f/1.4 Art: B&H Photo / Amazon / Adorama