Which should i choose, wordpress or wordpress mu

I would like to have an eshop with an affiliate option to make a percentage of profits but im not sure if all plug-ins work with wpmu or is it limited.i dont want to take the time to install wpmu if it is. but im willing to do either. Also im wondering if there is pluggings that allow multiple users to signup under different catagoreys, such as free- basic and advance memberships with eachone deciding what they can or cant see?