The biggest difference has to be personality, Faverolles are so strange and sweet, but that's one of my main reasons why I love them. Mine follow me around and try to come in the house on get in the car with me and stand at the door squawking to get in. The roosters are great, they are beautiful, gentle, but protective. My boyfriend loves our roos, he said they never had sweet roos like that when he grew up. Both of my boys have been babysitters for younger peeps and were adorable with them, trying to show them how to be a real chicken. Faverolles have a very different body, they have a low chest and are more stocky build. Their feathers are a lot fluffier looking and they are a natural auto sexing breed, so within a few weeks you will be able to tell if you have a roo or a hen due to their very different colors. They also have feathered legs and an extra toe. Faverolles are great winter layers of light brown/pinkish eggs and don't need any artificial lights on them. Our temperatures just dropped below 0 a couple weeks ago and my girls started laying. They are also a very old breed and may not be as prone to modern poultry diseases that affect the newer super breeds, I have read that somewhere, but am not 100% sure, maybe someone else has more info on that then I do. They have become rare, but are making a comeback in small backyard flocks.
You should try some, they are the best, 2 of my friends are hooked on them now after meeting mine lol