For camping shelter, a tent is my choice. With the family, as chaosmagnet said, this is an obvious choice. But even for backpacking with just us adults I prefer a tent. Not only does it seem more capable of handling various inclement weather scenarios but even that aside I like the privacy it affords over a tarp set-up.

For survival, I'd say tarp is the best choice from a size/packability perspective. For example, my daypack will usually have one of the All Weather Emergency blankets mentioned in another current thread. This allows for an improvised shelter in the case of emergency without incurring the cost of carrying a full blown backpacking set-up.