I actually agree that liberal Democrats are pretty similar to Democratic Socialists -- liberals have slightly more respect for the market. But a socialist is different. A socialist doesn't believe in private property, thinks workplaces should be "democratized" (meaning unions run everything), and depending on the branch of socialism, seems to think bureaucracy and democracy are synonyms.
Liberal Democrat: John Kerry, Barbara Boxer, Dick Durbin. Democratic Socialist: Paul Wellstone, Bernie Sanders, Dennis Kucinich. Socialist: George Bernard Shaw, Karl Marx, Eugene Debs. I don't like any of them, but there's a difference.
Yes, there is a difference. There are also differences between a '63, a '65 and a '67 Volkswagen, but just as in those cars, the differences are subtle, recognized by few, and all are headed in the same direction.