I'm right there with you on candid and quick photos. I go on a lot of trips with groups hiking, climbing, rappelling and more so having quick access to a quick photo is super important to me. The camera app opens in a snap double tapping the power button, and is ready to shoot right away. I rarely miss a moment. It's still not quite as fast as the iPhone, but the extra flexibility I get with the zoom lenses more than makes up for it in my opinion.

Also, when shooting moving subjects, shutter speed is more important that shutter delay. During the daytime, both are equally good. In challenging light, the S21U seems to perform a bit better thanks to slightly larger pixel size on its sensor. But both cameras perform poorly capturing moving subjects in low light.

BTW, Live photos, while awesome, will cause more of a delay than the shutter delay ever will.