I like 6x4 photos. Or, 6x4.5 if I use the default proportion on a digital camera. One or two fit nicely on a page, leaving me plenty of room to write my story or add embellishment. Printing photos at a standard size means I can get them all done in one batch, without having to think about resizing or cropping or anything complicated. Easy. The vast majority of my scrapbook pages use standard prints.
Every once in a while I take a photo that I really like and kind of want to show it off. But I am decorating-challenged (two and a half years and the walls in this house are still bare) so I print big photos and stick them in a drawer and forget about them. I had this picture from one of our walks in the spring, and decided to make the most of it. It hardly needs a scrapbook page; it's all photo.