Well, my perspective might be different than that of a student. However, what initially drew me to MHB is the active administration, and the well-written and actively enforced rules.
Also, the feeling of community here...the camaraderie between members is more inviting than at other math help sites that I have seen. There is more interest here from the staff to make MHB the best it can be and we are always looking for ways to improve. Many sites simply coast while we are always pushing forward to improve.
But these things may not really be of interest to a student who just needs help. We have an active and able set of helpers who rarely let a thread go without replies. Help is given promptly, courteously and usually judiciously, as we care to make the extra effort to actively engage the student as opposed to simply doling out solutions. This will appeal to the student who cares about learning as opposed to simply getting the assignment completed.
Among our helpers, we have a wide variety of experience and expertise.
But, think about what appeals to you as a student. You are likely more in touch with what students want and expect from a website now than a 50 year old man.