each vehicle model and gen typically has a particular forum which is the most visited (therefore the most knowledge).
E46 is E46fanatics
E46M is M3Forum
E53 X5 is Xoutpost
E90 is E90Post
F30 is ???
With the most active forums come all types of users, with some that frequent the Off-Topic and bring in the humor.
I never went on the Bimmerfest site. The users, info, etc.. never interested me in the 3 BMW's I've owned. If there was ever any useful information exclusive to that site, there was normally a link from the more popular site.