The chicken you buy from the store is around 6 to 8 weeks old. They are extremely tender and frankly pretty tasteless. The dual purpose chickens we raise and eat are butchered a lot older. They have more texture and more flavor. Someone used to the store chicken may not like the dual purpose because of either of these.
What they eat affects the flavor some but the real difference comes in age. The older the chicken the more flavor it has. The same is true of other meat animals we eat, such as pigs, lamb, or calves. The younger they are the more tender and less flavorful.
The older the chicken is the slower you cook it and the more moisture is required to take care of the texture. Pressure cookers and crock pots can be used to handle older birds but Cog au Vin is the traditional French way to turn an old rooster into a gourmet meal. Chicken and dumplings is a traditional southern comfort food using old chickens. Many people make stews with them. My standard method for old chickens, hens or roosters, is to bake them. I normally cut it into serving pieces, rinse those off but do not dry, coat with herbs like oregano and basil –use whatever you want, and bake in a ceramic baking dish that seals really well for maybe 4 hours at 240 degrees. I do that also for a fairly young cockerel or pullet but maybe at 250 degrees for 2-1/2 hours. It varies by age.