Hi
I'm considering buying new mirrorles
3 option
1. New sony A7RIII + 24-105
2. XT2 + 16mmF1.4, 35mmF1.4, 56mm F1.2
3. XT2 + 16-55F2.8
Purpose - street photography , landscape, architecture .
I think you may want a wider lens than 24mm equivalent for architecture. There are options in both systems, but you may want to factor this in. Also, 24-x zooms tend to have a lot of distortion at 24mm, which can be a pain for architecture.
Which do you think is better
I've used the a7rii recently and use the XT2. Given no one's used the a7riii for long, I hope I can help.
For large prints, the A7riii will have more resolution IF the 24-105 lives up to its billing. No one can say for sure, as the 24-105 hasn't been properly tested yet. Assuming it does, you will need to print very large or use an 8K screen to show the difference. Imaging resource have a print quality comparison which is useful for this purpose.
Set up two and three will have very similar IQ from about 16-35mm, but set up two may be slightly sharper in the edges. Set up 2 will be sharper at 55mm.
Low light performance is more important here. It would be tempting to say the a7riii would offer more dynamic range and low light performance, but this would be wrong. It will be similar to set up three and worse than set up two. Wide open, base ISO on the Fuji in set up 2 would compare to ISO 800 on the Sony, so around a 1 stop advantage to the Fuji.
2. quickness - AF/startup/ etc..
I'm not sure anyone can answer this until full tests of the a7riii are out. Given the amount at stake, I'd wait if you can. I suspect both will be good. I suspect the XT2 will have the edge for most C-AF applications but the Sony would trounce it for eye-AF.
The 35 f1.4 is slow to focus. Consider the 35 f2 if that's important.
The XT2 will be slightly lighter and noticeably smaller in configuration 3. It will be heavier in configuration 2, but each combination of lens and body will be significantly smaller and lighter.
Fuji has the edge here I think, having seen the Lens Rentals strip down of an a7sii. However, that's not a very good basis for comparing one to the other, so if anyone else knows more, ignore me.