The general consensus of powerlifters seems to be that since they put so much effort into their training and getting stronger, etc.--they don't have the energy and time to plan out their diet and cook chicken breasts/rice for every meal. They usually admit that they try to get 1g/lb of protein in but after that everything is open to them. As a result, most of these guys are fatasses. Especially anyone who competes in the 242lb class or higher. Now, the occasional genetic freak like Chabot or Bruner will still look like a BBer and have pretty low bodyfat, but this is due largely to genetics. I've seen Bruner's diet detailed and it is horrendous. It was something like this for a typical day:
Breakfast: 4 eggs, 2 cheese slices, can of Pepsi
Snack: 6 krispy kremes, pepsi
Lunch: 1 large papa john's pizza, pepsi
Snack 4 eggs, 2 cheese slices, Pepsi
Dinner: Spaghetti, green beans, pepsi
Snack: kripsy kremes, pepsi
So he is a genetic freak and is lean despite of his diet, not because of it. Many of these guys will tell you that elite athletes generally don't eat like bodybuilders, (ie they eat mcdonalds a lot and don't get a huge amount of protein or CLEAN carbs, etc) and that most guys who eat "correctly" are not good athletes. Well, it is unfortunately true as the number one aspect of success in strength sports and other sports is genetics. I guarantee you that 99% of people couldn't look like Bruner even if they did a ton of gear, worked out super hard and ate a perfect diet that was high in protein, EFA's, and had the perfect ratio of macronutrients etc. If you look at his diet, Bruner probably gets around 100g of protein a day and is a lean 260 last time I checked. He is the norm for top athelets, though. EVen the top olympians have appalling dietary practices. I remember hearing that Ben Johnson used to grub at Mickey D's twice a day and then would go out drinking every night even at his peak training stage of his career.
Anyway, most of the lower weight classes in PL have lean competitors because they have to make weight and hence they eat more protein and fewer carbs so they can't eat fast food very often.
Bodybuilders tend to overemphasize diet. Don't get me wrong, for the average man, diet is probably 30% of the picture. But as long as you get enough protein and enough EFAs, it doesn't matter if you eat burger/fries or chicken/rice most of the time. The total amount of calories is more important with regards to bodyfat than the composition of those calories. I think the glycemic index, complex carbs, and saturated fats are not going to make you fat (or keep you from being lean) unless you eat too much. Training, and genetics are the biggest factors, along with gear.