My family has had season passes at both Catamount and Butternut. Both were great family places where my kids learned. The snow making and grooming are better at Butternut. It's less prone to ice. The base is easier to navigate. The ski school is better. I disagree with the review that the trails are much longer at Catamount. The longest is 1 3/4 to 2 miles, tops. Butternut lets natural moguls form on at least one trail. The lodge is much larger and brighter at Butternut. Granted it is in a strange spot, 3/4's of the way up the bunny slope. Great Barrington beats Egremount apre-ski anyday.
On the downside, it does get busier on some weekends and lift lines tend to form at peak hours for the main lift. Catamount has several more challenging trails, especially the often icy Catapult. All and all they are quite comparable except on a busy weekend after a snowstorm, when I prefer Catamount.