If you want something fast growing to give a quick turn around as a meat bird, then go for one of the modern meat hybrids, as they will be your best option.
If you are looking for a dual purpose fowl, where the pullets will lay you eggs, and the hens when they have finished laying make a good big "boiling fowl", and all the cockerels you hatch which you don't need for breeding can be reared on for a meat bird, then I personally think that the English Cuckoo Marans, from a good utiltity line takes a lot of beating
A good strain will be productive layers (for a heavy traditional breed) and the beautiful colour of the eggs means they will always sell at a premium. Even one in a mixed box of eggs will increase sales
The spare boys should dress out at around 5-6+ lbs in 24 to 30 weeks, even fed on a basic ration of plain wheat as long as they have full free range. (Obviously they need the chick and grower ration till they are big enough to let out safely)
The meat is a real gourmet flavour, and of a fine white texture, and reared this way almost totally fat free.
I find my birds trouble free and healthy, with no propensity to peck, and even the boys live together happily with nothing more than an occasional squabble until they are ready to "go". Anyway - they get my vote
All the best
Sue