Berkshire vs Mohawk

This is for the American steam folks primarily. Being a steam guy for over fifty years, I feel stupid for asking this question, but I'm hitting the grind again tomorrow morning and don't have time to look up the information that somehow never occurred to me before tonight. What is the practical difference between the Berkshire and the Mohawk? A 2-8-4 vs 4-8-2. Specific examples for this question are 765 & 3001. Thanks