'Best platform' is a very broad term. Best in what way? In terms of ease of creation/coding? In terms of features/stability/reliability/scalability? Or what?
Be that as it may, if you're willing to explore the CMS route, I can vouch for WordPress with BuddyPress (and a handful of other) plug-ins. Proven, stable, feature-rich, quick to deploy etc. I'd say definitely worth checking out.