It's like a modern air force versus ancient foots soldiers. There's not really a competition. It's a just a matter of how long until the airborne forces of cellular technology finally stamp out ground-based landline phones for good.
For years, many families carried both services. They'd have cell phones for convenience and then use their traditional landlines as emergency backup (or for Internet service at home). Most younger consumers under the age of 30 don't see the point of paying for both landline and cell service, so nearly 70 percent don't have landlines at all. In an age when at least 90 percent of Americans have cell phones, landline numbers will only continue to dwindle [source: Sparshott].
All technologies change and evolve, even those like land-based telephone service, which has connected humans all over the planet for decades. No matter how important they may have been, they'll all eventually be replaced by something newer and more convenient.