I have a 34 large breed chickens. I use a sand/pea gravel mix in my run. The chickens do wind up scratching it in with the soil but there is never a smell or odor of any kind. Not even in wet, rainy weather and I live in deep East Texas. I think it also has to do with the fact that the run is built on higher ground so it doesn't hold water.
I keep the coop filled with pine shavings. I add a bag every month or so and it also never smells. i only clen it out once a year. I do not have to clean the run. The chickens also love to eat the smaller pebbles so I do not have to buy grit. i do however give them oyster shell.