If you don't keep up after them, they will stink (especially when the temps are above freezing). Accumulated chicken $h!t DOES stink. However, we've got a 100 square foot run for 9 chickens that has a mixed sand/native soil base that we throw straw in through the winter months and grass clippings in in during the mowing season. We rake out any leftover clippings and replace them weekly and we rake out all of the straw and replace that every 2-3 weeks; we get very little in the way of odors unless a chicken happens to drop a fresh cecal poo at your feet in 70+ deg weather.
Between our material and the fact that our run is under a second story porch and rarely gets rain/snow in it, the whole set up stays pretty dry all year round. The poo dries quickly, and so very little scent at all.
We floor our coop with several inches of pine shavings, which are changed weekly all year round. By the 5th/6th day after a change in high summer, the coop can get pretty ripe, but the shavings and a sprinkling of DE throughout the coop keep it in good shape.
As for the chickens themselves....if I grab a chicken and sniff it (and I can't deny having done so), they smell like dust 95% of the time. The other 5% of the time they smell like mud or poo, and that's only because they just ran through it!

We floor our coop with several inches of pine shavings, which are changed weekly all year round. By the 5th/6th day after a change in high summer, the coop can get pretty ripe, but the shavings and a sprinkling of DE throughout the coop keep it in good shape.
As for the chickens themselves....if I grab a chicken and sniff it (and I can't deny having done so), they smell like dust 95% of the time. The other 5% of the time they smell like mud or poo, and that's only because they just ran through it!