Aggregate function for a measure - Count or Sum

I have a cube for counting # of members in different ways. The measure is "Member Count", which is the count of records. I have two choices for creating the measure. Choice 1: In the fact table, create an integer column MemberCounter with default value as 1, and create the measure as the Sum() for MemberCounter;Choice 2: just create the measure as the Count() for any non-null column (like the Date column).I wonder which one is better performance-wise.