I am a member of both FCB and SCF, as well as other sites. I would say that FCB is the best "community" out there, mostly because of the Off Topic forum and the Baseball forum. SCF is much better with their trade boards.

Hopefully this will encourage each website to take the "best" from other sites and incorporate these bests into their own site. Both sites are great, both have their strengths and weaknesses, both will hopefully come out stronger.