My buddy swears by shooting at f/16 for sharp group shots, but I got way better results at f/8 last Saturday
We were at my niece's birthday party in Fresno and I took about 60 shots of the kids running around, and the f/8 ones came out way sharper than his f/16 ones. His theory is more depth of field equals more in focus, but mine is that the smaller opening made him crank the ISO to 6400 and everything got noisy and soft. So which side are you on, do you stop down all the way for a group or keep it open a bit and trust the focus?
Wait, are you sure the noise is what made his shots soft? Diffraction is the bigger issue at f/16, especially on crop sensors or smaller. Once you stop down past f/11 or so, light starts bending around the aperture blades and you actually lose sharpness, even with the ISO cranked down. So you're both kind of right, but the f/16 softness is probably diffraction first, noise second.