BEST ANSWER
I am a member of both the Garden State MLS (GSMLS) and the New Jersey MLS (NJMLS) and I can tell you with no doubt whatsoever that the primary MLS for Mahwah and Bergen County is the NJMLS. While both systems overlap into each other's areas somewhat, if you're looking for properties in Bergen County, its the NJMLS for the full listing inventory.
Trulia is different because Trulia gets it's listings from agents and real estate brokerage companies that choose to post their listings there. For example, let's say I have a listing at Ridge Gardens but I don't post my listings on Trulia and neither does my broker - well, they'll be in the NJMLS but they won't be on Trulia.
A MLS is a sharing of broker's listings. All the brokers in a specific georgraphic area agree to put every listing into a shared system called a Multiple Listing System. In other words, you have multiple numbers of listings from all the brokers going into 1 system that they can all access. Trulia is basically a private company that invites brokers to share their listings. Realtor.com gets it's listings from all of the MLS systems across the country which means that if you belong to a MLS system that doesn't send it's listings to Realtor.com, your listings won't be there but, in reality, almost every MLS does upload their listings to Realtor.com
Now, on the subject of Trulia, I believe that it is not only foolish but a lack of duty to the homeowner for any listing agent to not post their listings on Trulia. In fact, my company has been working on an automatic feed with Trulia so that our listings are posted here immediately. As you know, Trulia is a great site with tons of good information for buyers and sellers. I really think it's terrific and made sure my listings were posted here since it got going.
So, if you're dealing with, frankly, a lazy or technologically challenged listing agent, you won't see a home posted on Trulia while it is in the local MLS. And, if you're looking for properties in Bergen County, you'll find a smattering of them in another MLS but for all of them, go to http://www.NJMLS.com as well as Trulia.
Sun Jul 19 2009, 07:54