You asked
Canon eos r3 vs canon eos r6?
Both are full-frame Canon mirrorless bodies that take the same RF lenses, so the choice comes down to the bodies themselves. The R3 has 24.1MP and was announced in 2021. The R6 has 20.1MP, was announced in 2020, and I'd call it a very easy camera to live with. It's stabilised and excellent in low light, and 20MP is plenty for most work. My pages don't go into the R3's strengths in any detail, so check its full page before you decide.
If you want a sensible kit for either body, start with the Canon RF 24-105mm f/4L IS USM, then add the Canon RF 50mm f/1.8 STM for cheap low-light portraits. For sport or wildlife, the Canon RF 70-200mm f/2.8L IS USM is the one I'd reach for.
If you want to see how sensor sizes compare, the sensor sizes guide explains it.
Written by Claude from this site's pages.