FUJIFILM XF 100-400mm f/4.5-5.6 R LM OIS WR Lens - Any Good?

I've shot a fair amount on it, with Nikon, and with Nikon lenses adapted for Fuji.

The lenses render totally differently. Fuji seems to have a flatter, cuter image. Nikon is really contrasty and some of the birds look more scary with sharper edges. I could see this looking like the Nikon is sharper. But when I adapted the lens to Fuji I got the same look on the Fuji sensor.

The average pic seems nicer in the Nikon, but my favorites are often Fuji. Dustin Abbott mentioned in his review of the 70-300 too that even though it wasn't as sharp as the Sony the pictures were nicer.

Another thing I've been noticing more is Fuji seems to dial up the noise a lot on auto iso. Fuji will often pick 1600-3200 and Nikon will pick under 1000 for my neighborhood birding spot. I know there is a difference with the sensor size but it seems like part of that is Fuji's metering. Combined with Fuji iso noise not looking as good on Lightroom, I can see how people would say the lens isn't as sharp even when not looking at test charts.

Personally the issue I struggle with the most in a Fuji body is low light focusing, not the 100-400. It will just endlessly hunt. Even the cheap Nikon Z50 will cycle through the focus range but will pick something to focus on. This might be fixed with the XH2. With BIF on the Nikons I can usually make out a blob to focus on but with Fuji sometimes it's just a big blur and it never focuses on anything. Prefocusing on something at infinity helps. It was actually easier to deal with this with the 500 of because it was not focus by wire so I could move the focus ring to get out of the blurry mess. But since my Z9 came in I haven't really taken the XT4 for birding. Still undecided on if I am getting an XH2.