Hatchery barred Plymouth Rocks will generally be smaller than the breed standard, and lay a lot of eggs. Hatchery clean legged cuckoo Marans will also be smaller than the feather legged French Marans, and while their eggs will be a shade or two darker than the Rock's eggs, they won't be that nice dark brown/ chocolate that most French Marans, especially the black coppers, produce. For egg color variety, get French Marans. For high egg production, maybe the barred Rocks. Temperament will be individual, in my experience, not so much per breed.
Get some, try them out, and see what you like!
Mary
Get some, try them out, and see what you like!
Mary