I don't find the Facebook group anywhere near as useful as the forum. The Facebook Group is just a random dumping ground of stuff, where as here the topics are reasonably well organised into groups, so the bits that I'm not interested in - Bob Graham rounds, long distance stuff I can just ignore.
The Shropshire Fellrunning group is good. Relatively low traffic, but not much chaff to wade through. And no one asks what shoes to buy!