The two forums are very different despite both covering the subject of railways. As Rob says, each has its merits. There's a much higher percentage of making and practical chat on here.
The lack of wishlisting, moaning about the latest release and heated arguments on here are a breath of fresh air. You also get a lot of support on here when trying out new to you things. Researching prototype info and working out ways of replicating it doesn't end up with you being labelled a sad rivet counter and unlike the other place I've never been told I'm wasting my time.
That said, the current offline status of RMweb has reminded me just how much information is on the forum. Just about all my recent searches for info return a high percentage of RMweb thread hits, all of which are currently inaccessible. Hopefully it will get sorted with minimal damage.