Most of my images follow the 2x3 format (aspect ratio). Occasionally I would choose a square, but never really considered other aspect ratios or more importantly which aspect ratio fits which image. The 4x5 format provides a comfortable balance for my latest sunset buoy image taken near Bear Island, Northeast Harbor, Maine. I've added the un-cropped, un-editted image for comparison. Notice the empty space in the sky and water in the 2x3 crop. While the 4x5 crop has interesting textures throughout the entire image - my eyes continually move, rather than the 2x3 crop causing my view to drift to the top or bottom and stopping.
EXIF data: Nikon D800, 21mm, f/8, 1/125 sec, ISO 400, 7/15/15, 8:27 pM
Here is the 2x3 format (unedited) for comparison: