My experience is that the facebook groups are very active but that forums are a much more reliable source of knowledgeable help, insight and discussion. I am on several groups and forums, usually car related, and honestly some of the 'advice' on the facebook groups is complete tosh. Yes there are people on there who really know their stuff and they will be along and answer and advise, but not until loads of others have posted all sorts of 'advice' On forums you may wait a bit for a reply , but, if it's advice you need, the replies will be sensible !
I am a Noob to airsoft , although have several mates who have played for years, so will tend to lurk around the forum, using the search function lots ! As with any forum I am on, if I have something useful or helpful to contribute I will post, hopefully as my experience and knowledge grows I will be able to contribute more. This seems a genuinely friendly and enthusiastic forum to me.