One other thing to consider, besides the rational aspects to equity assignment, is fairness. People will talk about their equity allocation sooner or later and if there is a major differential between people who perceive themselves as similar (e.g., similar skills, similar job, came on board around the same time), it could hurt productivity and morale. People know the world isn't fair but they still get angry/demotivated when they are on the wrong end of the perceived unfairness.