Which of the new ault Rifles do veterans think is the best?

I'm a civilian, but one of the biggest issues with m16's and m4's is that as soon as they get dirty, they stop working, and when your in a firefight, that is one of the last things you want to happen. That is why the HK 416 would be my choice. I've seen videos of it being buried in mud and sand, as well as being placed in a bucket of water, and it was fired right after it came out. If the same things had been done to an m4 or an m16, they would've stopped working, and it would take hours to clean/dry them.