Functionally, within PBS, the difference is that Regular Membership comes with a vote in PBS elections. Associate Membership is required for a period and an application process that lets the Regular Members and council members get to know you a little better are the means to becoming a Regular Member. There are many Associates that remain as such for a variety of reasons. Associates and Regulars are not treated any different by anyone in my experience. But if you want to participate in the ballot votes Regular membership is required.