Doodledog
Bowls for most things, but plates if the food has to be cut up. Most of what we eat is forkable, so easier to eat from a bowl, and it keeps the food warmer, I think.
Macaroni cheese, curry, casserole - things like that are better in a bowl, IMO. Sunday roast (nut or meat), or fish and chips need plates, so you can cut the food as you eat it.
My only real 'rule' is that I only buy white crockery. I don't like seeing patterns under the food, and white will always (at least nearly) match other white things.
Snap! My crockery is all plain white, although different brands and styles. It is mostly bone china because that's much lighter, and I'm very miffed with John Lewis because they used to do a sort of basics range of bone china and have discontinued it. I have broken a few items and would like to have replaced them. White is white is white, so items from different ranges happily get used together.