Grassfed beef and wild caught fish are better because they are more nutrient-dense per calorie and don't contain the antibiotics that CAFO-raised animals do. Farmed salmon is a nasty gray color (color is added later) while wild caught salmon is a nice orange/pink. I think that says a lot about the health of the animal you are eating. Eating sick animals sick people.
I don't think there is anything wrong with eating chicken. At all. Do I think beef and lamb are healthier? Yea, but let's not let perfect be the enemy of good. Chicken is still healthy.
I think vegetables, squashes and tubers are healthier than nuts and seeds because they contain less anti-nutrients and are much more nutritious per calorie. Whole foods over processed is a no-brainer, except in rare exceptions (white rice vs brown rice, nixtamalized corn vs untreated corn, soaked nuts/legumes vs raw...of course it's up to you to decide if these are all whole foods).