Not necessarily. I said working dogs - not inbred Grand Champion Chihuahuas
. Although it gets more complicated if you're not going to take the example as it stands.
Mutt chickens - genuine mutts that you find in the back of Farmer Joe's shed - are going to be the healthiest chickens around and would be the longest lasting if Farmer Joe would feed more than cracked corn and would lock them up so the foxes didn't gobble them up. These chickens are healthy because they are regularly getting new blood into them (we'll assume Farmer Joe has to replace chickens regularly and brings in new blood
. They aren't coddled, so the weakest ones never get a chance to add their genes to the pool. They aren't bred for any special traits, so no one removes the most vigorous rooster or best hens because of poor markings or the wrong body type. But mutt chickens are also unpredictable. They may have a great, meaty body one generation, and the next generation be good layers with supbar breasts. This is because it's a "survival of the fittest/luckiest" rather than "survival of the traits I want."
Hatchery stock birds are mutts that are in a closed flock. A lot of hatcheries (I can think of two in my state alone *cough*) have flocks that never see new blood. These flocks may have been great stock ten or twenty years ago, but usually they are just recycling the same stuff over and over. When hatcheries need to they will cross breeds to get more of something rare, at which point you'll get new blood and a mutt bird that is then stuck in the same position as the other breeds: a closed flock of the wrong thing.
Breeders who are working with the breeds fall into two (main) categories. This is also where I'm going to get the most hate mail.
The first category of breeders are the ones working on show birds. Show birds are birds that breed true and are identical. That's what the show breeder wants: identical, perfect birds. That is what he is striving for. Oftentimes other traits will become less important: fast feathering, high egg production, large eggs, meaty body, etc. What the show breeder wants is to hatch 30 chicks and have all 30 chicks go to the Nationals because they are the best of the best of the best as far as physical type goes. When at the Nationals, no one asks whether this rooster was 4lbs at 20 weeks, or whether that hen laid at least 250 eggs in her first year: they focus solely on what the bird looks like. That is where you get what I liken to the AKC inbred show dogs. The ones that aren't bred for a purpose: they are bred specifically for looks.
I've found, in my personal experience, that show birds tend to be coddled too much to be of much use free ranging. They get sick easier, they lay fewer eggs, and they grow slower. Plus they are bullied relentlessly.
But they are absolutely beautiful.
The second category of breeders are more forgiving about looks. I liken them to people who raise working dogs. An AKC registered Great Pyrenees out of working lines looks a _lot_ different from one out of show lines. And people who breed working dogs want an animal that can perform, perform well for a long time (because it takes years to train), and maybe look really nice doing it. Working Border Collies may not have perfect markings, and a working Great Pyrenees doesn't have anything resembling a show coat - but they have the instincts and the ability to perform their job.
These breeders are looking for the traits that works for that breed. Someone may choose to keep a Buckeye rooster that is a perfect mouser over one that has the nicer comb, or may be more forgiving about that the angle of the tail on a Dominique hen that laid eggs while going through a heavy molt. They still want birds that fit the Standard of Perfection, but they aren't sacrificing the rest of the qualities that have made the breed so valuable over the years.
You'll find that people who breed for the traits and the looks will usually have a larger genetic pool because they aren't trying to perfect a single trait. And because a lot of people who breed this way want birds that can handle the cold or the heat or the rain; because of that they aren't coddled as much and they are going to be more resilient. Maybe not as rugged as Farmer Joe's mutts, but certainly more than the $200 pair of Wyandottes that are too nervous to step outside of their coop because they don't understand what this whole "mud" thing is about.
Technically there's probably a third category of people who are breeding show birds that are still useful. Those people may make it on the show table, but the odds aren't in their favor since it will take a lot more work to breed the perfect looking bird while being forgiving about other traits.
I really have no idea why I used dogs in this example since everyone on here is a chicken person, but I did
Also, these are broad sweeping examples. Not everyone will fit into these categories. I'm sure there are great show breeders out there who throw 200 juveniles out in a pen and the ones that survive are the ones he selects for grooming on the show table. And that there are many breeders who show their rugged birds with success. However, overall I've seen these two main camps when it comes to "serious" breeders and not just people who have a flock of such-and-such (because it's pretty) they occasionally sell eggs/chicks from.