While this is in no way comprehensive, here's some thoughts. For 1989 I'm largely drawing from Judt's "Postwar" and Stone's "The Atlantic and It's Enemies". 1848 from Albrecht-Carre's "A Diplomatic History of Europe Since the Congress of Vienna"

When thinking of the success or failures of the two revolutionary years it might be useful to think of them in terms of the success of the nationalism behind them. In both '48 and '89 nationalism represented a large part of what might be loosely called the spirit of the revolutions. In '48 the revolutions were mostly conducted within sovereign nation-states (Prussia, France, Austria, etc.) whereas in '89 you had a nations all under the control of a superpower (USSR). The long and short of it is that the revolutions of '48 failed because those who came into power (or left power such as Metternicht in Austria) were not all that different from those who came before. For instance, Napoleon III was not all that different, in broad terms, than Louie Phillipe and the Hohenzollerns remained in power in Prussia. Compared to '89 it was something of a "Meet the new boss same as the old boss" situation.

Contrast all of this to the situation in 1989 wherein the new leaders/systems of the nations of the Warsaw Bloc were markedly different from the Communist leadership. Power really returned to the individual nations. Certainly some of the movements, such as the Solidarity movement in Poland, were framed in Nationalistic terms to contrast the ideological terms the Communists had been using. And so, (again in a very non-comprehensive sense) the answer to your question is that '48 failed to fundamentally change much, while '89 did.