Fan pages are best for
crafting long-term relationships with fans, readers or customers. You can promote them with social ads and include apps."Unlike groups, fan pages are visible to unregistered people and are thus
indexed (important for reputation management, for example)," she says.
Facebook Groups on the other hand, are best for "hosting a (quick) active discussion and attracting quick attention," Smarty says. Marketers can send out bulk invites and recipients can pass them on en masse, making Groups a powerful viral platform.