Is drunkenness related to Blood Alcohol Level equally?

Obviously different people can get to different degrees of drunkenness by consuming different amounts of alcohol. My question: is a person’s BAL relative to his/her behavior. For example, Mark is a lightweight, he had two beers but he is slurring his speech and he is stumbling when he tries to walk. Mike, had three shots and and six pack, he is also slurring his speech and stumbling (equally as much as Mark). Is it likely that have an equal BAL?