I run 40 Cornish X in a 10x10 tractor. The thing with the Cornish X is that they don't have much desire to move or free range. They just sit around and eat all the time (I go 12 on, 12 hours off with the feed btw, because they will eat 24-7 if you let them and will develop leg problems.) They are processed at such a young age: 6-7 weeks males, 8-9 weeks females, before they have any raging hormones, so they get along extremely well even in such close quarters. The confined space is not filthy or inhumane if you are moving their tractor to fresh grass daily. Believe me...they have no desire to run away! I think tractoring the Cornish X is the best way to go. They poo--a lot!
Freedom Rangers I have not tried, but from what I understand, they are great for pasturing and will free range. They fill out a little slower too.
I think we began with 15 birds when we got started. It's a big process to butcher and can take all day when you're just learning. If you like them well enough, you'll have plenty of time over the summer to start another batch since they fill out so quickly.