We eat our extra Marans boys. In fact we had eating super speedy stew for dinner last night ( moral of this story, don't attack me or the dog) My experience is DH is addicted to salt, that the store chickens are soaked in, so they taste not as strong as store bought. I never remember exactly how old the roos are however, as they don't get separated into pens just stay in the main marans coop, but I aimed for 20 weeks. The last batch were olive eggers, and not as big, these marans boys are MUCH heftier. They are bread in France as a eating chicken.
Speedy was just under a year old, so he got stewed, but he was the best tasting of our extra chickens. But the only other heritage breed I have to compare it to are silkies, and the American ones are pretty small and delicate. Silkies, however a good fried, as long as black meat doesn't freak you right out.
I have a little rooster that got pecked in the head yesterday and still cant control his legs. I suspect some brain swelling. I'm giving him today to see if it gets better before we process him. I don't know who did it, we just had a ruckess under the deck before the large roos were out of rooster land so it might have been one of the girls. If we serve him to guests I will give you a report.