I did the broilers this past year. As someone else mentioned, they should be kept separate mainly because of feeding needs.
As stated by Welp hatchery - "You feed them normally for the first 5 days of age. At 7:00pm of the 5th day, make sure the broiler chicks are completely out of feed. That means there is positively no feed from 7:00 p.m. of the 5th day of age until 7:00 a.m. the following morning. You want them out of feed for 12 consecutive hours. Water, yes, but no feed for 12 hours. Continue this "minor feed restriction" program, removing the feed every night, until time of slaughter. Failure to follow this feeding program may result in heart attacks."
I also found, besides the feed restriction program, that they are very dirty compaired to the standard chickens. They eat more, so they poo more. That's the way it is. I only had 20, with more than enough room. Their coop/run got cleaned at least once daily...And it still stunk horribly, and I could barely keep the birds clean. The meat was great, but the raising them part was a pain.
Hope this answers your question.