You asked
Sigma 35mm f 1 4 dg dn art vs sirui aurora 35mm f 1 4?
Both are 35mm f/1.4 primes for full frame, both autofocus, and neither has stabilisation. They frame and handle depth of field the same way, so the real difference is which camera mounts they fit.
If you shoot Sony E or L-Mount, either works. The Sigma 35mm f/1.4 DG DN Art is the pick here, since it fits cameras like the Sony a7 III and the Panasonic Lumix S5. If you shoot Nikon Z or Fujifilm X, the Sirui Aurora 35mm f/1.4 is your only choice of the two. It fits the Nikon Z6 II and the Fujifilm X-T4, though on Fujifilm's APS-C bodies it frames like a 52mm lens.
If 35mm is your first fast prime, your first lenses explains where it fits in a kit, and portraits covers when it's the right focal length.
Written by Claude from this site's pages.