The Sigma ART 105 mm ƒ1,4 is simply amazing with a Fujifilm GFX camera. For unknown reasons, it works now much better with the Finger Pro EF-GFX adapter (and latest firmware). It practically never missed focus when i took 30 portraits of Sal after sunset. Remember that a GFX 50s II only provides contrast based AF. Yet, it worked surprizingly well. Not necessarily fast, but did it accurately.

It fascinates me, because I am normally not impressed with foreign lenses on a GFX camera via adapters.

Therefore I would say, that the Sigma ART 105/1.4 is almost par with the excellent Fujifilm GF 110mm F2 R LM WR, likely also in terms of (slow) AF. But the later is just a guess, not a true statement - because I can't compare. I don't have the Fujifilm GF 110/2

The only difference is, that the Sigma is absolutely huge and heavy 1.6 kilo lens, while the Fujifilm GF 110mm is sleeker (but still pretty large), and weights "only" 1 kilo.

Also i noticed that the Sigma gives much stronger cat shapes in the corners. That is, because it was never designed for a larger sensor. So, the corners can give an impression of "stuffed highlights / bokeh balls being squeezed". Which becomes at times pretty pronounced in photos where there are many highlight bokeh balls.