1) Chicken fat tends to be higher in omega-6s so I suppose on balance beef is healthier (even assuming both are pastured). However, if both are pastured, they're both good food sources. It would be a little easier to get your daily fat from beef due to the nature of the animal, and chicken fat is less saturated generally than beef fat, so I'd go with beef if I had to pick a staple. Again, calling one "healthier" than the other is somewhat misleading given that they're both pretty good.

2) Your weight day to day is very volatile and trying to blame a single meal for "massive" weight gain is not going to work. You drank more water and/or didn't lose as much to piss and insensible water loss overnight - you didn't really gain or lose a lot of weight over the course of a day because you ate chicken instead of beef. You can gain/lose pounds in a day just by changing your water balance.

You probably ate less fat than you thought because chicken is usually much leaner than beef, resulting in more hunger. Even a "lean" cut of beef typically has some marbling, so you end up consuming more fat than you would consciously notice. I've noticed the same thing - chicken being less satiating than a fatty steak - and I think this is probably the reason.

Doesn't chicken fat have a lot of PUF +omega 6 as mentioned above? (think I saw this mentioned on marksdailyapple when they talked about bone broths and how you'd probably want to skim the fat on chicken stock only because of its tendency to go rancid fast.)

Also along with the less saturated fat, and most chickens eat even more unnaturally than the cows do (as they are naturally omnivores, but are often put on the exact same all grain diets as the cows (vegetarians) are put on). Though if pastured in a real actual pasture they might of gotten enough insects to be a little better.

I'm also guessing the beef is more nutrient dense (more saturated fat, more minerals (iron, zinc etc)) which would also make it more satisfying.

But yes short answer go beef.

Long answer, the chicken probably was less calories, less good fats, less nutrient dense, and messed up your omega 3 to 6 ratio more than the beef would.

I think Girl Gone Primal hits on something here. Mode of preparation definitely affects satiety for me. For example, I can eat enormous amounts of scrambled eggs before I feel full. Hard-boiled eggs, not so much.

Now we're talking about next-day hunger here, but I do think the point stands.

I'm also willing to wager that the specific cut matters. For me, chicken breasts fill up far faster than thighs. The fat issue might be part of that, but I don't think it accounts for all of the effect.

BEEF- oz for oz Beef is the best food to eat. I just watched Food, Inc and I will never go near a chicken again- I don't see free-range coop free chickens as easy to buy as Grass fed beef that I can buy within my state.

Hunger is subjective and unreliable. There are way too many factors at play to just blame it on this food or that. Besides, a varied diet is always best. Eating primarily beef over chicken or vice versa is problematic. It is best to try and get protein from as many sources as possible. Makes me think of the body building types with tupperware containers of chicken breast day in and day out.

I don't know if you weight train, but beef also has a better amino acid profile for building muscle.