I tend to stick to smaller sizes -- 8x8 inch images on 9.5x12 paper is my most common, and that's with MF film. 35mm I tend to stick to smaller papers sizes like 8x10. Part of it's practical -- I'm far from being an advanced printer in the darkroom, so I still feel I'm in learning mode, and that it's more cost-effective to work with smaller sizes. Also, as I often have to work in community darkrooms, it's usually best to stick to papers that can easily fit in 11x14 inch trays (or smaller in many cases). Aesthetically though, I prefer smaller prints anyway -- I like getting up close and personal with prints (mine or others) and I can't really do that with larger sizes.