You asked
Leica sl3 vs sony a1 ii?
Both the Leica SL3 and the Sony a1 II are full frame mirrorless cameras announced in 2024, with stabilisation in the body. The main differences are the mount and the resolution. The SL3 has 60 megapixels on L-Mount, which gives you more room to crop and print large. The a1 II has 50.1 megapixels on Sony E, and that mount has a far bigger lens catalogue, so you'll have more choice and more used options.
If you go with the Leica, I'd pair it with the Leica APO-Summicron-SL 50mm f/2 ASPH for everyday work and the Leica Vario-Elmarit-SL 70-200mm f/2.8 ASPH for reach.
On the a1 II, the Sony FE 24-70mm f/2.8 GM II and the Sony FE 70-200mm f/2.8 GM OSS II make a strong pro kit that covers most work.
Written by Claude from this site's pages.