Asking what a "good dual purpose" is depends on which way you are leaning.
I like Orpingtons or Welsummers for primary egg layers and used occasionally as a table bird. Both are calm good egg lays and better than average on my table.
I really like Buckeyes for table birds. Superior eating qualities and they produce a decent quantity of eggs.
There are several dual-purpose breeds, but there's only ONE GOOD one, and that's the bbs Orpington. No, I am not prejudice! Well, maybe somewhat, but...