Hi, Geoff. I may be a little late answering your query, but I prefer the oval. My preference is based on the types of foods I cook. I often cook whole hams, chickens, turkeys. They, by nature, are quite oval rather than round. Therefore, I have oval cookware.
When it comes to soups, chili, stews, etc., they conform to the shape of the vessel in which they are cooked. In that respect, round, square, oval, hexagonal, doesn't really make any difference.
Just my take on your question.