I've had Red Rangers (from MMH) in the past and they were great. Very meaty but with good livability, and hens were decent layers of maybe 3-4 eggs a week. Very sweet and docile and easy to handle. They were ready for butcher at about 6-8 pounds at 14ish weeks. They didn't have the crazy double wide breast of a Cornish Cross, but they felt similar to my Standard Dark Cornish except rangierand longer legged. I bred some nice crossbreeds with them as my DP roosters as well. Only word of warning if you keep any for breeding, do not keep the cocks with other breeds of hens. They're fine with other Red Rangers but they will crush standard laying hens... learned that the hard way.
Cornish Cross CAN be kept out to 14 weeks... but it's not pretty. Out of 10 birds 5 couldn't walk by 14 weeks and 2 more were having serious trouble getting around. 2 were healthy as could be and I almost considered keeping one to see if she might be breedable. I had them professionally processed by a local guy because I had to go out of town. He threatened to charge me the turkey price if I ever brought those monsters to him again...