You asked
Should I upgrade from the leica sl2 s?
Honestly, only if you're running into a specific limit. The SL2-S is 24 megapixels and is the one I'd pick for low light and video. If you're cropping heavily or printing large and need more detail, the Leica SL2 is the step up. It has a 47-megapixel full frame sensor, in-body stabilisation and a weather-sealed body.
If your pictures are already sharp and you're happy with the low-light and video results, I'd keep what you have and spend the money on glass instead. Before you buy anything, check that the body takes the lenses you already own. The SL2-S page lists the L-Mount lenses it works with.
If you do decide to move up, buying used is the cheapest way to do it. A camera one generation old often gives you most of the performance for much less.
Written by Claude from this site's pages.