There is still some debate but it seems Fan pages are winning out because of the additional things you can do with them.

Some say Groups are better for hosting a (short-term) discussion and attracting quick attention. But the consensus is that Groups are better for creating long-term relationships with your fans, readers or customers.

First and foremost the 2 major differences include:

1. Unlike groups, fan pages are visible to unregistered people and are thus indexed (important for reputaion management, for example);
2. Unlike pages, groups allow to send out “bulk invite” (you can easily invite all your friends to join the group while with pages you will be forced to drop some invites manually). Groups are thus better for viral marketing, meaning that any group member can also send bulk invites to the friends of his.

Now let’s go into some details: