I am a newbie to raising chickens. Last year I did Cornish/X and a few slow broilers. This year I am about four weeks into Colored Rangers. I also have a few breeds for eggs. I think all the chickens smell the same. The amount of odor is equal to the pounds of live chicken. The only difference is that the heavier chickens put down more poop per day so it has less chance to compost or dry out. I also believe that there are several different "strains" of Cornish/X. They have slightly different characteristics. If you read some of the commercial web sites (the ones providing the eggs to the hatcheries) you can see that even within one company they have different strains with different pros/cons. Unfortunately it is probably hard for someone raising 25 birds to find out which hatchery buys and hatches which strain. My Cornish/X's foraged just as much as my Colored Rangers, although a few folks said that mine might start ranging a bit more as they get older. At this point, other than the color, the only difference I see is that several (not all) of the Colored Rangers are aggressive toward the other chicks, especially the egg chicks. My Cornish/x would push to get to the food but they never pecked one another. I would favor the Colored Rangers if it is true that the white birds are more prone to hawk attack. Many of you are much more experienced raising meat birds but since this is Backyardchickens I thought I'd throw in my 2 cents.