The only thing I can think of in terms of 'bigger is better' is that if someone is able to make a print that is six by eight feet large, then it is more difficult to do than one that is six by eight inches. It takes a more accomplished printer, and a totally different setup of a darkroom to do that.

Other than that, I prefer prints that aren't extremely large either. My own pinhole series of waterfronts has evolved from little 6x6" prints, to 8x8" on 11x14" paper, and I have finally decided they need to be 13x13" on 16x20" paper. One at a time I'm slowly making my way to the whole portfolio being done that way.
At the same time I have a slew of portraits that I just wouldn't want to print any larger than 6x8" on regular 8x10" paper. If I was offered money from a buyer to make them bigger I could (gotta eat too), but most of them I like best as small prints.

My own summarized opinion is that the subject matter dictates the print size.

The other side of it is to enjoy the pictures others have made, regardless of their size. I stand back to view very large prints, and I creep in closer to look at smaller works. All of them are equally enjoyable to me, as long as the photograph is one I enjoy to begin with.

- Thomas