I am both a member here, and a senior moderator at macfora. While there is something to what Inline_guy says, I would like to point out that the frivolous posting mostly takes place in the Lounge, where we encourage 'chatter' about any old thing, as long as it stays PG-13 in topic and language. The other forums are for 'serious' topics. Whenever someone posts with a question, knowledgable people do their best to answer quickly and correctly, just as they do here. Whenever someone posts news, tips, tricks, etc. it is done the same way as here again. Sometimes Macfora's 'first with the news', sometimes Macosx.com is.
Preferring one site to another is only natural. Some like it one way, some another. Of course most of us will be at one more than the other, but there is nothing preventing dual membership.
Just my $.02.