Is Berkshire Hathaway too big for significant returns?

Hey,

I like BRK and think they run a nice business. But I have a concern, that I wanted to ask you guys about:

Is Berkshire too big to outperform in the long run?

Now I know, that they can and probably will grow for a long time to come. But still, it must get harder and harder to find good deals, that significantly boost the value.