Here is my experience with both guru and incgamers. I love to look up information on tactics/builds/strategies/missions on guru. A lot of very experienced players have spent a lot of time putting up good information on the site. However, if you want some input on an idea or have a question or just want to throw out a comment and not be flamed and made to feel stupid, this is the site for you. The mods do a great job of keeping things nice. I like this site enough to have just joined as a PAL and pay actual money to support it after being on it for a year.
I could say a few things about the Mods over at The Guru and one in particular.That board is to heavily modded and as to many Admins.Their Mods think they know it all which is not the case here.
I don't have much experience with Guru, only thing I can say is that new information arises much faster over there than here. (Probably due to the fact that there are much more active users on guru). And from what I've seen, the people there often write before they think.
I've come here my entire guildwars career (six years now, this is a new account), and I like it very much. It used to be more active, a few years back. Now, mostly the regulars post, and I know what to expect from them. So its nice and familiar here.