What type of rice is good for using in soups?
I like to stay with long-grain rices because they are less sticky than short-grain ones. I also cook the rice separately so it doesn't over-absorb the liquid. Too, soup is a great way of using up leftover rice. Whenever I make rice, I always make twice as much as I need at the moment because I can find an interesting way of using the leftovers.
I like the heartiness of brown rice in my soups. Short grain brown rice is kind of barley-like and great in vegetable soups. Like boulangere, I cook mine separately but sometimes will simmer the cooked rice in the soup for a little while to thicken the soup and soften the grain.
If the recipe calls for uncooked rice in the soup, the liquid will include the amount that the rice will absorb while cooking. If you use precooked rice, be sure to adjust the liquid you add.
I like medium grain white rice. usually found in the spanish section of the store
For me, this is an issue where variety gives us different options, not better or worse. I've made minestrone-type soups and added short, fat risotto rices and found them wonderful. In other cases, I want the long, less sticky effect. Wild rice (not really a rice) is great in other soups.
More of a grain than rice but barley or farro are wonderful additions and stand up well in soups.