The first is that we possess the truth, the fullness of faith. Second, in a sense we're the new kids on the block. Not only are they surprised we're there, but they're pleased with our low-key approach. They realize we aren't going to pressure them. As a result, we're treated courteously and are routinely invited to return.
Catholics have another advantage - our salvation theology.
Many sects believe Catholics in particular are damned precisely for being Catholics. They know they may not have another chance to talk to the people who answer the doors, so they try to get attention right now. This means our approach need not seem so urgent. Of course, our theology shouldn't lead us into complacency, nor should it cause us to avoid opportunities to ask people to commit themselves, but we don't have to strong-arm them. We're able to be authentically neighborly, extending warm welcomes and trusting that the Holy Spirit will work through us when and how he sees fit.