Digital Slrs Comparison Excellent Book From Digital And Slr Angles! Is There A Reason Digital SLRs Are Typically High Quality Then Regular Digital Cameras?

Is there a reason digital SLRs are typically high quality then regular digital cameras? - digital slrs comparison excellent book from digital and slr angles!

I understand the basic mechanisms, such as the mirror that lets you see exactly what the picture is taken, but should not completely obsolete digital display? It is the only reason why SLR cameras are better because they have a broader and higher costs?