I feel like it depends on your diet and macro intake, chicken is leaner and has a lower calorie to protein ratio than beef so you can eat more volume with lower calories, it is generally easier to digest and it doesn't make you feel as full so if you are eating several meals a day chicken may make it easier to get your meals down without feeling bloated. Beef as you said is more nutrient rich containing more iron, zinc, b12 and creatine but it has a higher calorie to protien ratio because it is not as lean as chicken so the fat content can ad up fast depending on the cut. And with lipids already taking a hit from the gear the higher fat content in beef can push the ldl and triglycerides even higher. For me I feel like a mix between the two but a little heavier on the chicken works good for me, chicken throughout the day and for my meal closer to my workout so I don't feel bloated at the gym and beef later in the afternoon for dinner so I feel fuller at night and im not tempted to snack, and occasionally pork for dinner though not very often because I just don't like pork very much but my wife and kids get sick of chicken and beef every day. I think if you are bulking you can lean a little harder on beef or bison for your protein if you are cutting or looking for a slower lean bulk go heavier on chicken or turkey for your protein but a combination is good for variety so you don't get board with your food.