I cannot really agree with either of these views. Of the two, I think that pluralism is closer to being accurate in the United States today. However, I share Schattschneider's view that the "heavenly chorus" that the pluralists talk about "sings with a strong upper-class accent."
While Mills' view of a power elite may have been accurate when he wrote, I do not believe it is true any longer. I do not think that the various elites of the business world and the political world and the military world are as interconnected as they may have been in the 1950s. I think our society is too large and open for that to be the case any more.
However, pluralism is a little bit naive as well. There is no way that all groups have equal access to the political system. Those groups that have money and power will have a much better chance at influencing the system on most issues than their opponents who have less money and power. Therefore, the "playing field" is nowhere near as level as scholars like Robert Dahl might argue.
So, I would argue that the power elite idea is outdated and that the pluralist idea is closer to the truth. However, I would argue that the pluralist model fails to recognize the advantages held by those interest groups that are rich and powerful.