I weigh and monitor my chickens because I love to! I am newer to chicken keeping and trying to learn everything I can about them right now. Since I don't know how much a Cornish X chick should weigh each week or what they are supposed to look like, I am doing this monitoring so that I can learn those things. I am a person that likes to learn the ins and outs of everything I do, so I can do it the best that I can possibly do it.Weighing chicks and monitoring them the way you are describing is overkill. There is no benefit from it. The free range birds are definitely a 100% improvement in taste and quality.
Try this test. Buy one from the store, and cook it along side the one you free range. Put them in the 'fridge and the next morning the store bought one will be covered in fat, while the free range will still look good and lean, but still have the same amount of meat. Free range is the way to go, and if that's not possible, then large enclosure with scratch grains and grower fed sparingly, is a gret second best.
Good luck
Chicken Tin (Alaska)
I am also monitoring everything I spend taking care of them so that I know how much I will charge when friends want to buy chickens from me. It is also super awesome to know that I spend less raising my own meat birds than I would spend buying cruddy commercial chickens at the grocery store!
I'm sure I won't continue the weighing and documenting as time goes on and I learn these things. But for now, I am learning and I can share the information with others on this site that are new and learning too. I love that!