Nowadays, it is rare for developers to market/sell the projects themselves. Most of them now sub the marketing to reputable agency companies. If a project has 1000 units, developers will usually divide the units amongst several agencies and depending on which units the purchasers hooked on, that agency takes the cake.

It's somewhat the developer's evil plan to create competitive hence boosting their sales because every agency is going to incite purchasers to buy the units parked under their agency instead.

Whatever it is, there is no real significant difference here because the agency merely acts as a liaison. You get the same thing as you would from the developer or maybe even better because agents may give you a slight edge of the purchase price from their cut of the commission.

To me, the best thing to go through an agency is that you get them to do you bidding.

I got my unit through a an agency and managed to forced to get me a parking near the lift lobby when the developer refuses to accommodate to my requests XD