My experience with this: At first I went with a frame that was 'just right' -- neither too large nor too small, but dead center, and toured on that bike for a few years. Then I tried a larger frame -- one size up from the standard version of 'just right' -- and toured quite a bit on that frame. Then I went one size down -- one size below the 'just right' frame. And then bought a few other bikes that were either in the middle or on the large side.

I am most comfortable touring on the medium and smaller frames. Larger frames tend to be a bit awkward, especially in off-road situations. They feel somewhat bulky and clumsy. The smaller frames are more tossable, controllable, and maneuverable.

That said, I do like the longer wheelbases of the larger bikes, in a way, for cruising. But some of the mid-sized (for me) bikes have geometry that makes them handle like longer bikes. So they are fine.

The smaller bikes are more fun to ride, in my experience.

My suggestion would be to avoid going too large -- better to find something that is either right on or smaller.

Bruce Gordon has a lot of experience fitting bikes, and has mentioned that many people seem to (mistakenly) lean toward frames that are too large. He suggests going smaller, and giving it a month or so, with an open mind. He says that many people have thanked him for steering them in the direction of smaller frames.

John Schubert has written about similar experiences of his own.

From what you have said, my guess is that the advice that is steering you toward 56 is steering you large, and that 54 would be better than 56, and much better than 58.