Buckeyes as well as many other breeds can make a great dual purpose flock, if they're bred to the breed standard. In my opinion, good Cornish are the ultimate meat bird, but were never intended to be a dual purpose breed.
I already have some nice Orpingtons that would fill the bill of a very good dual purpose and winter hardy flock if I wanted. [Though the cockerel's comb got frost bit last winter, and he is now re-homed with a friend that was looking for a large, meaty bird to cover his flock of mixed hens.] However, I'm wanting a larger, blue/green egg layer that can be processed at an early age [maybe 12 weeks for a small carcass with heavy meat suitable for cooking whole on the grill]. I would like to see them develop meat at the same rate they grow their frame; allowing me to process a good looking but smaller carcass very early, or letting them grow out to a larger yet still tender carcass when processed at a more conventional age. If I wanted, I could cull one of these April hatched CX crosses today and have a small but nicely shaped bird sitting on my table tonight. I have some slightly older purebred Ameraucana juveniles that are visually as large, but there is so little meat under their feathers that I they would look terrible dressed, and hardly worth the time and effort to process.